Table saws with safety systems and systems to mount and index attachments

ABSTRACT

Table saws and table saws designed to implement safety systems that detect contact between a person and a dangerous portion of the saw are disclosed. Table saw components, mounting systems for table saws, and table saw attachments are also disclosed. One embodiment may include a first clamp surface, a second clamp surface spaced apart from the first clamp surface so that a base portion of a riving knife or splitter can be placed between the clamp surfaces with the opposing sides of the base portion generally parallel to the first and second clamp surfaces.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation of U.S. patent application Ser. No.13/964,390, filed Aug. 12, 2013, which is a continuation of U.S. patentapplication Ser. No. 12/927,196 filed Nov. 8, 2010, issuing as U.S. Pat.No. 8,505,424 on Aug. 13, 2013, which is a continuation of U.S. patentapplication Ser. No. 11/045,972 filed Jan. 28, 2005, issued as U.S. Pat.No. 7,827,890 on Nov. 9, 2010, which in turn claimed the benefit of andpriority from U.S. Provisional Patent Application Ser. No. 60/540,377filed Jan. 29, 2004. The disclosures of these applications are herebyincorporated by reference in their entireties.

TECHNICAL FIELD

This specification relates to table saws. More particularly, thisspecification relates to safety systems for table saws, to mountingsystems for table saw attachments, and to table saw attachments such asriving knives, blade guards, splitters and anti-kickback devices.

BACKGROUND

A table saw is a power tool used to cut a work piece to a desired sizeor shape. A table saw includes a work surface or table and a circularblade extending up through the table. A person uses a table saw byholding a work piece on the table and feeding it past the spinning bladeto make a cut. The table saw is one of the most basic machines used inwoodworking.

The blade of a table saw, however, presents a risk of injury to a userof the saw. If the user accidentally places their hand in the path ofthe blade, or if their hand slips into the blade, then the user couldreceive a serious injury or amputation. Accidents also happen because ofwhat is called kickback. Kickback may occur when a work piece contactsthe downstream edge of the blade as it is being cut. The blade thenpropels the work piece back toward the user at a high velocity. Whenthis happens, the user's hand may be carried into the blade because ofthe sudden and unexpected movement of the work piece

Safety systems or features are often incorporated into table saws tominimize the risk of injury. Probably the most common safety feature isa guard that physically blocks an operator from making contact with theblade. In many cases, guards effectively reduce the risk of injury,however, there are many instances where the nature of the operations tobe performed precludes using a guard that completely blocks access tothe blade.

Another safety device sometimes incorporated into table saws is a rivingknife. A riving knife is a fin-like plate positioned adjacent the rearedge of the saw blade and within the projected kerf and top-to-bottomcutting capacity of the blade. A riving knife functions to keep a workpiece from shifting sideways and catching on the rear edge of the bladeand being kicked back at the user by the blade. The riving knife ismounted in a table saw so that it remains in a fixed position relativeto the blade as the blade tilts and changes elevation.

Some table saws include a spreader or splitter instead of a rivingknife. A splitter is a flat plate, similar to a riving knife, buttypically extending above the top-to-bottom cutting capacity of theblade so that a blade guard can be mounted thereto. An anti-kickbackdevice such as anti-kickback pawls, which are toothed pawls positionedto oppose a work piece being thrown back toward a user, are oftenmounted on the splitter. Splitters typically tilt with the blade, but donot move up and down with the blade.

Other safety systems have been developed to detect when a human bodycontacts a predetermined portion of a machine, such as detecting when auser's hand touches the moving blade on a saw. When that contact isdetected, the safety systems react to minimize injury. These systems maybe used in conjunction with table saw attachments such as blade guards,riving knives, splitters and anti-kickback pawls.

The present document discloses improved table saws, table sawcomponents, systems to mount and index table saw attachments, and tablesaw attachments such as riving knives, blade guards, splitters andanti-kickback pawls.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic block diagram of a machine with a fast-actingsafety system.

FIG. 2 is a schematic diagram of an exemplary safety system in thecontext of a machine having a circular blade.

FIG. 3 shows a table saw.

FIG. 4 shows a right-side view of the internal mechanism of the sawshown in FIG. 3.

FIG. 5 shows a left-side view of the internal mechanism of the saw shownin FIG. 3.

FIG. 6 shows a front view of the internal mechanism of the saw shown inFIG. 3.

FIG. 7 shows a back view of the internal mechanism of the saw shown inFIG. 3.

FIG. 8 shows a top view of the internal mechanism of the saw shown inFIG. 3 with the table removed.

FIG. 9 shows a bottom view of the internal mechanism of the saw shown inFIG. 3.

FIG. 10 shows a front-right perspective view of the internal mechanismof the saw with the table removed.

FIG. 11 shows a front-left perspective view of the internal mechanism ofthe saw with the table removed.

FIG. 12 shows a back-right perspective view of the internal mechanism ofthe saw.

FIG. 13 shows a back-left perspective view of the internal mechanism ofthe saw.

FIG. 14 shows a right-side view of a trunnion brace used in the sawshown in FIG. 3.

FIG. 15 shows a top view of a trunnion brace used in the saw shown inFIG. 3.

FIG. 16 shows a left-side view of a trunnion brace used in the saw shownin FIG. 3.

FIG. 17 shows part of the internal mechanism of the saw with a portionlabeled “A” designated for a detailed view.

FIG. 18 is the detail view of the portion labeled “A” in FIG. 17,showing part of a tilt control mechanism.

FIG. 19 shows part of the internal mechanism of the saw with a portionlabeled “B” designated for a detailed view.

FIG. 20 is the detail view of the portion labeled “B” in FIG. 19,showing part of a tilt control mechanism.

FIG. 21 shows a right-side view of an elevation plate and elevationsystem.

FIG. 22 shows a left-side view of an elevation plate and elevationsystem.

FIG. 23 shows a top view of an elevation plate and elevation system.

FIG. 24 shows a bottom view of an elevation plate and elevation system.

FIG. 25 shows a perspective view of an elevation plate and elevationsystem with portions labeled “C” and “D” designated for detail views.

FIG. 26 is the detail view of the portion labeled “C” in FIG. 25,showing part of an elevation system.

FIG. 27 is the detail view of the portion labeled “D” in FIG. 25,showing part of an elevation system.

FIG. 28 is a perspective top view of part of the internal mechanism ofthe saw shown in FIG. 3, including an elevation plate and arborassembly.

FIG. 29 is a bottom view of the components shown in FIG. 28.

FIG. 30 is a right-side view of part of the internal mechanism of thesaw shown in FIG. 3, including an elevation plate, arbor assembly, brakecartridge and blade.

FIG. 31 is a left-side view of part of the internal mechanism of the sawshown in FIG. 3, including an elevation plate, arbor assembly, brakecartridge, blade and arbor block support mechanism.

FIG. 32 shows an arbor block and arbor used in the saw shown in FIG. 3.

FIG. 33 shows a portion of the internal mechanism of the saw shown inFIG. 3, with a portion labeled “E” designated for a detail view.

FIG. 34 is the detail view of the portion labeled “E” in FIG. 33,showing an arbor block support mechanism.

FIG. 35 shows an arbor block support mechanism.

FIG. 36 also shows an arbor block support mechanism.

FIG. 37 shows an eccentric bushing.

FIG. 38 shows two eccentric bushings end-to-end.

FIG. 39 shows shafts used in the elevation system of the saw shown inFIG. 3.

FIG. 40 is a different view of the portion of the elevation system shownin FIG. 39.

FIG. 41 is a top view of the portion of the elevation system shown inFIG. 39.

FIG. 42 is a perspective, right-side view of an elevation plate.

FIG. 43 is a perspective, left-side view of the elevation plate shown inFIG. 42.

FIG. 44 shows a table saw with a riving knife.

FIG. 45 shows a side view of the table saw shown in FIG. 44 with thecabinet and other parts removed for clarity.

FIG. 46 shows a top, perspective view of the saw shown in FIG. 45.

FIG. 47 shows a top, perspective view of the saw shown in FIG. 45 withthe table removed.

FIG. 48 shows a riving knife.

FIG. 49 shows another view of a riving knife.

FIG. 50 shows a mounting system or clamp for table saw attachments.

FIG. 51 shows another view of the mounting system shown in FIG. 50.

FIG. 52 shows a top view of the mounting system shown in FIG. 50.

FIG. 53 shows a cross-section view of the mounting system shown in FIG.50 taken along the line 1-1 in FIG. 52.

FIG. 54 shows a mounting plate used in the mounting system shown in FIG.50.

FIG. 55 shows another view of the mounting plate shown in FIG. 54.

FIG. 56 shows a positioning plate used in the mounting system shown inFIG. 50.

FIG. 57 shows another view of the positioning plate shown in FIG. 56.

FIG. 58 shows still another view of the positioning plate shown in FIG.56.

FIG. 59 shows a clamping plate used in the mounting system shown in FIG.50.

FIG. 60 shows another view of the clamping plate shown in FIG. 59.

FIG. 61 shows still another view of the clamping plate shown in FIG. 59.

FIG. 62 shows a cam bushing used in the mounting system shown in FIG.50.

FIG. 63 shows another view of the cam bushing shown in FIG. 62.

FIG. 64 shows still another view of the cam bushing shown in FIG. 62.

FIG. 65 shows yet another view of the cam bushing shown in FIG. 62.

FIG. 66 shows a handle used in the mounting system shown in FIG. 50.

FIG. 67 shows still another view of the handle shown in FIG. 66.

FIG. 68 shows yet another view of the handle shown in FIG. 66.

FIG. 69 shows a saw assembly without a cabinet or table but with ariving knife installed in a mounting system.

FIG. 70 shows a detailed view of a section F from FIG. 69 with part ofthe mounting system removed.

FIG. 71 shows the mounting system of FIG. 50 in an open position.

FIG. 72 shows another view of the mounting system of FIG. 50 in an openposition.

FIG. 73 shows a top view of a table saw with a table insert removed.

FIG. 74 shows a blade guard assembly.

FIG. 75 shows another view of the blade guard assembly shown in FIG. 74.

FIG. 76 shows still another view of the blade guard assembly shown inFIG. 74.

FIG. 77 shows yet another view of the blade guard assembly shown in FIG.74.

FIG. 78 shows a top view of the blade guard assembly shown in FIG. 74.

FIG. 79 shows a bottom view of the blade guard assembly shown in FIG.74.

FIG. 80 shows a front view of the blade guard assembly shown in FIG. 74.

FIG. 81 shows a back view of the blade guard assembly shown in FIG. 74.

FIG. 82 shows a support arm used in the blade guard assembly shown inFIG. 74.

FIG. 83 shows a spreader or splitter used in the blade guard assemblyshown in FIG. 74.

FIG. 84 shows a blade shroud used in the blade guard assembly shown inFIG. 74.

FIG. 85 shows another view of the blade shroud used in the blade guardassembly of FIG. 74.

FIG. 86 shows a pivot pin used in the blade guard assembly shown in FIG.74.

FIG. 87 shows a pivot connection used in the blade guard assembly shownin FIG. 74.

FIG. 88 shows another view of the pivot connection shown in FIG. 87.

FIG. 89 shows a blade guard assembly mounted in a saw assembly.

FIG. 90 shows a detailed view of a section G from FIG. 89 with part of amounting system removed.

FIG. 91 shows a nut used in the blade guard assembly shown in FIG. 74.

FIG. 92 shows a spacer used in the blade guard assembly shown in FIG.74.

FIG. 93 shows a blade guard assembly mounted in a saw assembly with theblade guard up.

FIG. 94 shows a splitter and anti-kickback device used in the bladeguard assembly shown in FIG. 74.

FIG. 95 shows a two-piece table insert.

FIG. 96 shows a top view of the table insert shown in FIG. 95.

FIG. 97 shows a bottom view of the table insert shown in FIG. 95.

FIG. 98 shows the right portion of the table insert shown in FIG. 95.

FIG. 99 shows another view of the right portion of the table insertshown in FIG. 95.

FIG. 100 shows still another view of the right portion of the tableinsert shown in FIG. 95.

FIG. 101 shows the left portion of the table insert shown in FIG. 95.

FIG. 102 shows another view of the left portion of the table insertshown in FIG. 95.

FIG. 103 shows still another view of the left portion of the tableinsert shown in FIG. 95.

DETAILED DESCRIPTION

A machine that incorporates a safety system to detect and react to adangerous condition, such as human contact with a designated portion ofthe machine, is shown schematically in FIG. 1 and indicated generally at10. Machine 10 may be any of a variety of different machines, such astable saws, miter saws, band saws, jointers, shapers, routers, hand-heldcircular saws, up-cut saws, sanders, etc. Machine 10 includes anoperative structure 12 having a working or cutting tool 14 and a motorassembly 16 adapted to drive the cutting tool. Machine 10 also includesa safety system 18 configured to minimize the potential of a seriousinjury to a person using the machine. Safety system 18 is adapted todetect the occurrence of one or more dangerous conditions during use ofthe machine. If such a dangerous condition is detected, safety system 18is adapted to engage operative structure 12 to limit any injury to theuser caused by the dangerous condition.

Machine 10 also includes a suitable power source 20 to provide power tooperative structure 12 and safety system 18. Power source 20 may be anexternal power source such as line current, or an internal power sourcesuch as a battery. Alternatively, power source 20 may include acombination of both external and internal power sources. Furthermore,power source 20 may include two or more separate power sources, eachadapted to power different portions of machine 10.

It will be appreciated that operative structure 12 may take any one ofmany different forms. For example, operative structure 12 may include astationary housing configured to support motor assembly 16 in drivingengagement with cutting tool 14. Alternatively, operative structure 12may include one or more transport mechanisms adapted to convey a workpiece toward and/or away from cutting tool 14.

Motor assembly 16 includes at least one motor adapted to drive cuttingtool 14. The motor may be either directly or indirectly coupled to thecutting tool, and may also be adapted to drive work piece transportmechanisms. The particular form of cutting tool 14 will vary dependingupon the various embodiments of machine 10. For example, cutting tool 14may be a single, circular rotating blade having a plurality of teethdisposed along the perimetrical edge of the blade. Alternatively, thecutting tool may be a plurality of circular blades, such as a dado bladeor dado stack, or some other type of blade or working tool.

Safety system 18 includes a detection subsystem 22, a reaction subsystem24 and a control subsystem 26. Control subsystem 26 may be adapted toreceive inputs from a variety of sources including detection subsystem22, reaction subsystem 24, operative structure 12 and motor assembly 16.The control subsystem may also include one or more sensors adapted tomonitor selected parameters of machine 10. In addition, controlsubsystem 26 typically includes one or more instruments operable by auser to control the machine. The control subsystem is configured tocontrol machine 10 in response to the inputs it receives.

Detection subsystem 22 is configured to detect one or more dangerous ortriggering conditions during use of machine 10. For example, thedetection subsystem may be configured to detect that a portion of theuser's body is dangerously close to or in contact with a portion ofcutting tool 14. As another example, the detection subsystem may beconfigured to detect the rapid movement of a workpiece due to kickbackby the cutting tool, as is described in U.S. patent application Ser. No.09/676,190, the disclosure of which is herein incorporated by reference.In some embodiments, detection subsystem 22 may inform control subsystem26 of the dangerous condition, which then activates reaction subsystem24. In other embodiments, the detection subsystem may be adapted toactivate the reaction subsystem directly.

Once activated in response to a dangerous condition, reaction subsystem24 is configured to engage operative structure 12 quickly to preventserious injury to the user. It will be appreciated that the particularaction to be taken by reaction subsystem 24 will vary depending on thetype of machine 10 and/or the dangerous condition that is detected. Forexample, reaction subsystem 24 may be configured to do one or more ofthe following: stop the movement of cutting tool 14, disconnect motorassembly 16 from power source 20, place a barrier between the cuttingtool and the user, or retract the cutting tool from its operatingposition, etc. The reaction subsystem may be configured to take acombination of steps to protect the user from serious injury. Placementof a barrier between the cutting tool and teeth is described in moredetail in U.S. Patent Application Publication No. 2002/0017183 A1,entitled “Cutting Tool Safety System,” the disclosure of which is hereinincorporated by reference. Retracting the cutting tool is described inmore detail in U.S. Patent Application Publication No. 2002/0017181 A1,entitled “Retraction System for Use in Power Equipment,” and U.S. patentApplication Ser. No. 60/452,159, filed Mar. 5, 2003, entitled“Retraction System and Motor Position for Use With Safety Systems forPower Equipment,” the disclosures of which are herein incorporated byreference.

The configuration of reaction subsystem 24 typically will vary dependingon which action or actions are taken. In the exemplary embodimentdepicted in FIG. 1, reaction subsystem 24 is configured to stop themovement of cutting tool 14 and includes a brake mechanism 28, a biasingmechanism 30, a restraining mechanism 32, and a release mechanism 34.Brake mechanism 28 is adapted to engage operative structure 12 under theurging of biasing mechanism 30. During normal operation of machine 10,restraining mechanism 32 holds the brake mechanism out of engagementwith the operative structure. However, upon receipt of an activationsignal by reaction subsystem 24, the brake mechanism is released fromthe restraining mechanism by release mechanism 34, whereupon, the brakemechanism quickly engages at least a portion of the operative structureto bring the cutting tool to a stop.

It will be appreciated by those of skill in the art that the exemplaryembodiment depicted in FIG. 1 and described above may be implemented ina variety of ways depending on the type and configuration of operativestructure 12. Turning attention to FIG. 2, one example of the manypossible implementations of safety system 18 is shown. System 18 isconfigured to engage an operative structure having a circular blade 40mounted on a rotating shaft or arbor 42. Blade 40 includes a pluralityof cutting teeth (not shown) disposed around the outer edge of theblade. As described in more detail below, braking mechanism 28 isadapted to engage the teeth of blade 40 and stop the rotation of theblade. U.S. Patent Application Publication No. 2002/0017175 A1, entitled“Translation Stop For Use In Power Equipment,” the disclosure of whichis herein incorporated by reference, describes other systems forstopping the movement of the cutting tool. U.S. Patent ApplicationPublication No. 2002/0017184 A1, entitled “Table Saw With ImprovedSafety System,” U.S. Patent Application Publication No. 200210017179 A1,entitled “Miter Saw With Improved Safety System,” U.S. PatentApplication Publication No. 2002/0059855 A1, entitled “Miter Saw withImproved Safety System,” U.S. patent Application Publication No.2002/0056350 A1, entitled “Table Saw With Improved Safety System,” U.S.Patent Application Publication No. 200210059854 A1, entitled “Miter SawWith Improved Safety System,” U.S. Patent Application Publication No.2002/0056349 A1, entitled “Miter Saw With Improved Safety System,” U.S.Patent Application Publication No. 2002/0056348 A1, entitled “Miter SawWith Improved Safety System,” and U.S. Patent Application PublicationNo. 2002/0066346 A1, entitled “Miter Saw With Improved Safety System,”U.S. Patent Application Publication No. 2003/0015253 A1, entitled“Router With Improved Safety System,” U.S. Patent ApplicationPublication No. 2002/0170400 A1, entitled “Band Saw With Improved SafetySystem,” U.S. Patent Application Publication No. 2003/0019341 A1,entitled “Safety Systems for Band Saws,” U.S. Patent ApplicationPublication No. 2003/0056853 A1, entitled “Router With Improved SafetySystem,” U.S. Provisional Patent Application Ser. No. 60/406,138,entitled “Miter Saw With Improved Safety System,” and U.S. ProvisionalPatent Application Ser. No. 60/496,550, entitled “Table Saws With SafetySystems,” the disclosures of which are herein incorporated by reference,describe safety system 18 in the context of particular types ofmachines.

In the exemplary implementation, detection subsystem 22 is adapted todetect the dangerous condition of the user coming into contact withblade 40. The detection subsystem includes a sensor assembly, such ascontact detection plates 44 and 46, capacitively coupled to blade 40 todetect any contact between the user's body and the blade. Typically, theblade, or some larger portion of cutting tool 14 is electricallyisolated from the remainder of machine 10. Alternatively, detectionsubsystem 22 may include a different sensor assembly configured todetect contact in other ways, such as optically, resistively, etc. Inany event, the detection subsystem is adapted to transmit a signal tocontrol subsystem 26 when contact between the user and the blade isdetected. Various exemplary embodiments and implementations of detectionsubsystem 22 are described in more detail in U.S. Patent ApplicationPublication No. 2002/0017176 A1, entitled “Detection System For PowerEquipment,” U.S. Patent Application Publication No. 2002/0017336 A1,entitled “Apparatus And Method For Detecting Dangerous Conditions InPower Equipment,” U.S. Patent Application Publication No. 2002/0069734A1, entitled “Contact Detection System for Power Equipment,” U.S. PatentApplication Publication No. 2002/0190581 A1, entitled “Apparatus andMethod for Detecting Dangerous Conditions in Power Equipment,” U.S.Patent Application Publication No. 2003/0002942 A1, entitled “DiscreteProximity Detection System,” U.S. Patent Application Publication No.2003/0090224 A1, entitled “Detection System for Power Equipment,” andU.S. Provisional Patent Application Ser. No. 60/533,791, entitled“Improved Detection Systems for Power Equipment,” the disclosures ofwhich are all herein incorporated by reference.

Control subsystem 26 includes one or more instruments 48 that areoperable by a user to control the motion of blade 40. Instruments 48 mayinclude start/stop switches, speed controls, direction controls,light-emitting diodes, etc. Control subsystem 26 also includes a logiccontroller 50 connected to receive the user's inputs via instruments 48.Logic controller 50 is also connected to receive a contact detectionsignal from detection subsystem 22. Further, the logic controller may beconfigured to receive inputs from other sources (not shown) such asblade motion sensors, work piece sensors, etc. In any event, the logiccontroller is configured to control operative structure 12 in responseto the user's inputs through instruments 48. However, upon receipt of acontact detection signal from detection subsystem 22, the logiccontroller overrides the control inputs from the user and activatesreaction subsystem 24 to stop the motion of the blade. Various exemplaryembodiments and implementations of control subsystem 26, and componentsthat may be used in control system 26, are described in more detail inU.S. Patent Application Publication No. 2002/0020262 A1, entitled “LogicControl For Fast Acting Safety System,” U.S. Patent ApplicationPublication No. 2002/0017178 A1, entitled “Motion Detecting System ForUse In Safety System For Power Equipment,” U.S. Patent ApplicationPublication No. 2003/0058121 A1, entitled “Logic Control With Test Modefor Fast-Acting Safety System,” U.S. Provisional Patent Application Ser.No. 601496,568, entitled “Motion Detecting System for use in a SafetySystem for Power Equipment,” and U.S. Provisional Patent ApplicationSer. No. 60/533,598, titled “Switch Box for Power Tools with SafetySystems,” the disclosures of which are all herein incorporated byreference.

In the exemplary implementation, brake mechanism 28 includes a pawl 60mounted adjacent the edge of blade 40 and selectively moveable to engageand grip the teeth of the blade. Pawl 60 may be constructed of anysuitable material adapted to engage and stop the blade. As one example,the pawl may be constructed of a relatively high strength thermoplasticmaterial such as polycarbonate, ultrahigh molecular weight polyethylene(UHMVV) or Acrylonitrile Butadiene Styrene (ABS), etc., or a metal suchas fully annealed aluminum, etc. It will be appreciated that theconstruction of pawl 60 may vary depending on the configuration of blade40. In any event, the pawl is urged into the blade by a biasingmechanism in the form of a spring 66. In the illustrative embodimentshown in FIG. 2, pawl 60 is pivoted into the teeth of blade 40. Itshould be understood that sliding or rotary movement of pawl 60 mightalso be used. The spring is adapted to urge pawl 60 into the teeth ofthe blade with sufficient force to grip the blade and quickly bring itto a stop.

The pawl is held away from the edge of the blade by a restrainingmechanism in the form of a fusible member 70. The fusible member isconstructed of a suitable material adapted to restrain the pawl againstthe bias of spring 66, and also adapted to melt under a determinedelectrical current density. Examples of suitable materials for fusiblemember 70 include NiChrome wire, stainless steel wire, etc. The fusiblemember is connected between the pawl and a contact mount 72. Preferably,fusible member 70 holds the pawl relatively close to the edge of theblade to reduce the distance the pawl must travel to engage the blade.Positioning the pawl relatively close to the edge of the blade reducesthe time required for the pawl to engage and stop the blade. Typically,the pawl is held approximately 1/32-inch to ¼-inch from the edge of theblade by fusible member 70, however other pawl-to-blade spacings mayalso be used.

Pawl 60 is released from its unactuated, or cocked, position to engageblade 40 by a release mechanism in the form of a firing subsystem 76.The firing subsystem is coupled to contact mount 72, and is configuredto melt fusible member 70 by passing a surge of electrical currentthrough the fusible member. Firing subsystem 76 is coupled to logiccontroller 50 and activated by a signal from the logic controller. Whenthe logic controller receives a contact detection signal from detectionsubsystem 22, the logic controller sends an activation signal to firingsubsystem 76, which melts fusible member 70, thereby releasing the pawlto stop the blade. Various exemplary embodiments and implementations ofreaction subsystem 24 are described in more detail in U.S. PatentApplication Publication No. 2002/0020263 A1, entitled “Firing SubsystemFor Use In A Fast-Acting Safety System,” U.S. Patent ApplicationPublication No. 2002/0020271 A1, entitled “Spring-Biased Brake Mechanismfor Power Equipment,” U.S. Patent Application Publication No.2002/0017180 A1, entitled “Brake Mechanism For Power Equipment,” U.S.Patent Application Publication No. 2002/0059853 A1, entitled “Power SawWith Improved Safety System,” U.S. Patent Application Publication No.2002/0020265 A1, entitled “Translation Stop For Use In Power Equipment,”U.S. Patent Application Publication No. 2003/0005588 A1, entitled“Actuators For Use in Fast-Acting Safety Systems,” and U.S. PatentApplication Publication No. 2003/0020336 A1, entitled “Actuators For UseIn Fast-Acting Safety Systems,” the disclosures of which are hereinincorporated by reference.

It will be appreciated that activation of the brake mechanism willrequire the replacement of one or more portions of safety system 18. Forexample, pawl 60 and fusible member 70 typically must be replaced beforethe safety system is ready to be used again. Thus, it may be desirableto construct one or more portions of safety system 18 in a cartridgethat can be easily replaced. For example, in the exemplaryimplementation depicted in FIG. 2, safety system 18 includes areplaceable cartridge 80 having a housing 82. Pawl 60, spring 66,fusible member 70 and contact mount 72 are all mounted within housing82. Alternatively, other portions of safety system 18 may be mountedwithin the housing. In any event, after the reaction system has beenactivated, the safety system can be reset by replacing cartridge 80. Theportions of safety system 18 not mounted within the cartridge may bereplaced separately or reused as appropriate. Various exemplaryembodiments and implementations of a safety system using a replaceablecartridge, and various brake pawls, are described in more detail in U.S.Patent Application Publication No. 200210020261 A1, entitled“Replaceable Brake Mechanism For Power Equipment,” U.S. PatentApplication Publication No. 2002/0017182 A1, entitled “Brake PositioningSystem,” U.S. Patent Application Publication No. 2003/0140749 A1,entitled “Brake Pawls for Power Equipment,” and U.S. Provisional PatentApplication Ser. No. 601496,574, entitled “Brake Cartridges for PowerEquipment,” the disclosures of which are herein incorporated byreference.

While one particular implementation of safety system 18 has beendescribed, it will be appreciated that many variations and modificationsare possible. Many such variations and modifications are described inU.S. Patent Application Publication No. 2002/0170399 A1, entitled“Safety Systems for Power Equipment,” U.S. Patent ApplicationPublication No. 2003/0037651, entitled “Safety Systems for PowerEquipment,” and U.S. Patent Application Publication No. 2003/0131703 A1,entitled “Apparatus and Method for Detecting Dangerous Conditions inPower Equipment,” the disclosures of which are herein incorporated byreference.

A table saw adapted to implement features of the safety systemsdescribed above is shown at 100 in FIG. 3. Saw 100 is often called acabinet saw or a tilting-arbor saw. The saw includes a table 102 onwhich a work piece may be cut. The table is supported by a cabinet 104.A blade 105 (labeled in FIGS. 4 through 7) extends up through an opening106 in the table and a blade guard 108 covers the blade. Hand wheels 110and 112 may be turned to adjust the elevation of the blade (the heightthe blade extends above the table) and the tilt of the blade relative tothe tabletop, respectively. In operation, a user turns the hand wheelsto position the blade as desired and then makes a cut by pushing a workpiece on the table past the spinning blade.

FIGS. 4 through 7 show various views of the internal mechanism of saw100. FIGS. 8 through 13 show additional views of the internal mechanismof the saw, but with the table removed. The remaining figures showvarious components and mechanisms that may be used in the saw.

Table 102 is bolted onto a front trunnion bracket 120 and a backtrunnion bracket 122 by bolts 124 (the bolts are shown best in FIGS. 10through 13). The trunnion brackets, in turn, are bolted onto andsupported by cabinet 104 through holes such as hole 107 shown in FIG. 8.The cabinet is constructed to support the weight of the table and theinternal mechanism of the saw. Alternatively, table 102 could be secureddirectly to the cabinet or some other support instead of to thetrunnions.

It is important for the table to be positioned properly relative to theblade. Typically, the front edge of the table should be as perpendicularto the plane of the blade as possible in order to make straight, squarecuts. There are many mechanisms by which the position of the tablerelative to the blade can be adjusted. FIGS. 4, 5, and 13 show one suchmechanism. A pin 210 extends up from a flange in rear trunnion bracket122, as shown in FIG. 13. That pin is positioned substantially in theside-to-side center of the rear trunnion bracket. Pin 210 extends upinto a corresponding socket on the underside of the back edge of thetable and the table is able to pivot around the pin. Table 102 includestwo holes 212, one in the right front side of the table and one in theleft front side, as shown in FIGS. 4 and 5. A bolt is threaded into eachof those holes and extends through the side of the table. Holes 212 arepositioned so that when the bolts are threaded through the holes, theends of the bolts abut the right and left sides of the front trunnionbracket, respectively. Those sides are labeled 213 in FIG. 8. Threadinga bolt farther into its hole will cause the bolt to push against thefront trunnion bracket and the table will then pivot around pin 210.Thus, the position or squareness of the table relative to the blade canbe adjusted by threading the bolts into holes 212 a desired amount.

Saw 100 also includes front and rear trunnions 126 and 128. Thesetrunnions are supported in the saw by the front and rear trunnionbrackets, respectively. Each trunnion bracket includes an arcuate tongueor flange 130 (best seen in FIGS. 10 through 13), and the front and reartrunnions each include a corresponding arcuate groove 132 (grooves 132are labeled in FIGS. 10 and 12). Trunnion brackets 120 and 122 supporttrunnions 126 and 128 by flanges 130 extending into correspondinggrooves 132. In this manner, the flanges provide a shoulder or surfaceon which the trunnions may rest. The arcuate tongue and grooveconnections also allow the trunnions to slide relative to the trunnionbrackets. When the trunnions slide on the trunnion brackets, the bladeof the saw tilts relative to the tabletop because the blade is supportedby the trunnions, as will be explained below.

A trunnion brace 134 extends between and interconnects the front andrear trunnions so that the trunnions move together. The trunnion bracealso holds the front and rear trunnions square and prevents thetrunnions from moving off flanges 132 when the mechanism is assembled.The trunnion brackets, trunnions and trunnion brace are shown isolatedfrom other structure in FIGS. 14 through 16.

The trunnions and trunnion brace are tilted relative to the trunnionbrackets by gears. A rack gear 136 is cut into an edge of front trunnion126, and a worm gear 138 is mounted on front trunnion bracket 120 tomesh with the rack gear. This arrangement is shown in detail in FIGS. 17through 20. Worm gear 138 is mounted on a shaft 140 and the shaft issupported in a bracket 142. A collar 143 holds the shaft in place in thebracket. Bracket 142 is bolted onto front trunnion bracket 120 by bolts144. The bolts pass through oversized holes in the front trunnionbracket and thread into holes in bracket 142. The oversized holes in thefront trunnion bracket allow for adjustment of the position of bracket142 up or down relative to the rack gear. Being able to adjust theposition of the bracket up or down is important in order to make surethe rack and worm gears mesh properly. Of course, the oversized holesmay be in bracket 142 and the threaded holes may be in the fronttrunnion bracket.

Other mechanisms also may be used to align worm gear 138 with rack gear136. One such mechanism is one or more eccentric bushings that holdshaft 140 in bracket 142. The bushings may be turned to move shaft 140and worm gear 138 toward or away from rack gear 136 to make sure thegears mesh properly. A possible eccentric bushing is shown in FIG. 37 at146. The bushing includes a hole 148 positioned off-center from thelongitudinal axis of the bushing, a hex head 150 to allow a person toturn the bushing, and shoulders 152. The bushing is configured so thattwo such bushings may be positioned end to end, as shown in FIG. 38, andshaft 140 may be supported in the resulting hole 148. When the bushingsare positioned in bracket 142, turning either of the two hex heads 150with a wrench will cause both bushings to turn because shoulders 152abut, and turning the bushings will cause shaft 140 and worm gear 138 tomove toward or away from rack gear 136 because hole 148 is off center.

Shaft 140 extends out through a hole in cabinet 104 and hand wheel 112is mounted on the shaft. When a user turns hand wheel 112 and shaft 140,worm gear 138 meshes with rack gear 136 causing the trunnions to moveand the blade to tilt relative to the tabletop. A plate 154 is bolted tobracket 142 and extends up past rack gear 136, as shown in FIG. 18, tohelp prevent the bottom of front trunnion 126 from moving away from thefront trunnion bracket and to help maintain the rack gear and worm gearin position.

Stops 155 and 156, shown best in FIG. 6, limit the distance that thetrunnions and trunnion brace may move. Stop 155 comprises a boltthreaded through a shoulder in the front trunnion bracket and a lock nutto hold the bolt in place. The bolt is positioned so that it will abut aside edge of the front trunnion bracket when the front trunnion is atone limit of its movement, as shown in FIG. 6. Stop 156 comprises a boltthreaded into a hole in the front trunnion bracket (also shown in FIG.25). A lock nut or some other means may be used to hold the bolt inplace. The bolt is positioned so that the front trunnion will abut thehead of the bolt when the front trunnion is at the opposite limit of itsmovement. The distance the trunnions may move can be adjusted bythreading the bolts in stops 155 and 156 in or out, as desired.

Saw 100 typically includes a label 157 mounted on the front of thecabinet. Label 157 includes angle demarcations to indicate the degreethe blade tilts relative to the tabletop. A pointer 158 is mounted on oradjacent shaft 140 to point to the angle demarcations on label 157. Forinstance, when the blade is tilted 45 degrees relative to the tabletop,pointer 158 would point to the 45 degree mark on label 157. In thedepicted embodiment, pointer 158 is mounted to the front trunnion,adjacent shaft 140.

Saw 100 also includes an elevation carriage shown as elevation plate170. The elevation plate is supported by the front and rear trunnionsand tilts with the trunnions. The blade is supported on the elevationplate, as will be described, so tilting the elevation plate causes theblade to tilt. The elevation plate is also configured to move up anddown relative to the trunnions. Moving the elevation plate up and downis what causes the blade to move up and down relative to the tabletop.

Elevation plate 170 includes two bores 180 and 182, labeled in FIG. 42.A bushing 184, which may be made from oil impregnated bronze, fits intoeach bore and is held in place by screws and washers 185. The washersoverlap the edge of the bushing to prevent the bushing from moving outof the bore. A support shaft 172 fits into bores 180 and 182, as shownin FIGS. 21 through 26, and elevation plate 170 is free to slide up anddown on the shaft. Shaft 172 is bolted onto front trunnion 126 toconnect the elevation plate to the front trunnion. In the depictedembodiment, shaft 172 fits into two notches 174 in front trunnion 126.Bolts 176 and 178 then secure the shaft to the front trunnion, as shownin FIGS. 39 through 41. Bolt 176 extends through shaft 172 and threadsinto a hole in the front trunnion. Bolt 178 extends through the fronttrunnion and threads into shaft 172. In this manner the shaft issecurely anchored to the front trunnion. Shaft 172 may be mounted to thefront trunnion in other ways as well.

The distance elevation plate 170 may slide up and down on shaft 172 isultimately defined by the spacing between notches 174 on front trunnion126 and the spacing between bores 180 and 182 on the elevation plate.That distance, however, may be further defined by adjustable stops 186shown in FIG. 42. These stops are made of bolts threaded through holesin the elevation plate and lock nuts to hold the bolts in place, asshown. The bolts are positioned so they abut a shoulder 188 extendingout from the front trunnion bracket, as shown in FIG. 21. (Shoulder 188is also shown in FIGS. 39 and 41.) The distance the elevation plate mayslide up or down on shaft 172 is thus defined by how far the stops orbolts extend.

Elevation plate 170 also includes a threaded bore 190 configured toaccept a threaded shaft 192, shown best in FIGS. 21, 28 and 39. Shaft192 also extends through a bore 193 in shoulder 188 on the fronttrunnion bracket to further support the shaft (bore 193 is labeled inFIGS. 15 and 41). The threaded shaft may be held in bore 193 in anymanner, such as by clips or collars. A bevel gear 194 is mounted on theend of shaft 192 below shoulder 188. A second bevel gear 196 is mountedon a shaft 198 that extends perpendicularly relative to shaft 192. Shaft198 extends through and is supported for rotation by the front trunnion.A collar 200 holds shaft 198 in place. Shafts 192 and 198 are positionedso that the two bevel gears mesh. Shaft 198 also extends through a holein cabinet 104 and hand wheel 110 is mounted on the shaft. When a personturns hand wheel 110, bevel gear 196 causes threaded shaft 192 to turn.When threaded shaft 192 turns, elevation plate 170 moves up or down onthe shaft because hole 190 is threaded. Moving the elevation plate upand down causes the blade to move up and down relative to the tabletop.In this manner, a user may adjust the elevation of the blade.

The construction of elevation plate 170 and shafts 172 and 192 may bereferred to as a vertical slide because the elevation plate slidesvertically on shaft 172. Other constructions of vertical slides are alsopossible, such as using one or move dovetail slides instead of a shaft.Multiple vertical shafts may also be used instead of one shaft andmultiple vertical shafts may be spaced apart to support the elevationplate. Shafts or dovetail slides may also be positioned at each end ofthe elevation plate instead of at one end only.

Additionally, a motor may be used instead of hand wheel 110 to turn thebevel gears to raise or lower the elevation plate, or a motorized liftmay be used instead of the bevel gears. The motor or lift may beactuated by a typical switch or by a switch configured to be similar toa hand wheel.

Elevation plate 170, and any components attached to the elevation plate(such as a motor, as will be discussed below), may have significantweight and therefore it may be difficult to turn hand wheel 110 to raisethe blade. Accordingly, the depicted embodiment includes a gas spring202 mounted at one end to the elevation plate and at the other end to abracket 204 mounted to the front trunnion, as shown best in FIGS. 25 and26. The gas spring is biased to push the elevation plate up with apredetermined amount of force to make it easy for a user to turn handwheel 110 to raise the blade. The force of the gas spring may beselected so that the elevation plate is biased up or down to take outany play or slack between threaded shaft 192 and threaded bore 190.Forces in the range of 50 to 250 pounds may be used, depending on howmuch weight must be lifted.

It is important that elevation plate 170 be restricted from anyside-to-side motion or rotation around the longitudinal axis of supportshaft 172 in order to hold the saw blade straight, and support shaft 172and threaded shaft 192 limit how the elevation plate may move. However,in the depicted embodiment, because the elevation plate is relativelylong and supported principally at one end, and also because ofmanufacturing tolerances in shafts 172 and 192 and their correspondingbores in the elevation plate, there is a risk that the elevation platemay move slightly in an undesired manner, especially if the elevationplate is tilted. Accordingly, elevation plate 170 includes bores 220 and222 in two projections at the distal end of the elevation plate,opposite bores 180 and 182, and a guide shaft 224 is mounted in thebores. The guide shaft may be held in the bores by clips, bolts, or anyother method.

A guide block 226 is placed on the guide shaft between bores 220 and 222so the shaft can move up and down in the guide block. The guide block,in turn, is mounted to the apex of a V-bracket 228, and the opposite twoends of the V-bracket are bolted to the rear trunnion 128, as shown inFIGS. 25 and 27. This arrangement allows the elevation plate to move upand down to change the elevation of the blade, but prevents the distalend of the elevation plate from moving to the side or rotating aroundshaft 172 because the V-bracket is bolted to the rear trunnion and theguide block is mounted to the V-bracket.

This arrangement also accommodates variances or tolerances inmanufacturing. Guide shaft 224 should be substantially parallel withsupport shaft 172 so that the elevation plate can move up and down onshaft 172 without binding on shaft 224. However, it may be difficult tomake shaft 224 substantially parallel with shaft 172, especially giventhat the shafts are spaced a significant distance apart.

In the depicted embodiment, guide shaft 224 may be mounted in aneccentric bushing 230. Bushing 230 is similar to bushing 146 shown inFIG. 37, except it does not need shoulders 152. Bushing 230 has anoff-center hole through which guide shaft 224 passes. The bushing isplaced over the shaft and in bore 222 and held on the shaft by a clip.The bushing may then be turned to move the guide shaft and align theshaft as necessary. When the bushing is turned to its desired location,it is held in place by a set screw 232 shown in FIG. 27.

Guide block 226 is bolted onto the apex of V-bracket 228, as explained.A single bolt mounts the guide block to the V-bracket so the bracket canbe adjusted or rotated around the bolt to align with the guide shaft sothe guide shaft can slide up and down in the guide block.

The two ends of V-bracket 228 opposite the guide block are bolted to therear trunnion by bolts 234, as stated. The V-bracket itself is made of amaterial which has some flex, such as metal, and there is a distancebetween bolts 234 and guide block 226. That distance and the flex of thematerial allow the V-bracket to flex out toward the rear of the saw ifnecessary to accommodate the guide shaft. That flex may be necessary ifthe distance of shaft 224 from shaft 172, the position of shaft 172 orshaft 224 in the saw, or the dimension of other components in the sawvaries due to manufacturing tolerances or other reasons. That flex alsomay be necessary to accommodate the expanding or contracting of theelevation plate due to temperature changes. Thus, the ability of theV-bracket to flex out helps prevent the guide shaft from binding inguide block 226.

This mounting configuration may be thought of as constraining only onedegree of freedom of the guide shaft; specifically, it constrains anyside-to-side movement of the guide shaft. The mounting configurationallows the guide shaft and elevation plate to move up and down andfront-to-back. This mounting configuration accommodates somemisalignment of the guide shaft.

An arbor block 240 is pivotally mounted to the elevation plate as shownin FIGS. 28 and 29. The arbor block includes two projections 244 and246, each projection having a bore 248, as shown in FIG. 32. Theelevation plate includes a raised portion 250 and bore 243 extendsthrough that raised portion, as shown in FIG. 43. Projections 244 and246 on the arbor block sandwich raised portion 250, and a shaft 242 thenpasses through bores 248 in the arbor block and bore 243 in theelevation plate to mount the arbor block to the elevation plate. Arborblock 240 may then pivot up and down around shaft 242.

An arbor 251 is mounted for rotation in arbor block 240, as shown inFIGS. 28 and 32, and the blade of the saw is mounted on the arbor sothat it spins when the arbor rotates. The arbor is held in two bearingsthat are mounted in bearing seats in the arbor block. The bearings areisolated electrically from the arbor block by plastic overmolding on thearbor or by insulating bushings. Electrodes are positioned adjacent butnot touching the arbor to impart the electrical signal to the blade usedin the detection subsystem discussed above. The configuration of thearbor and electrodes are disclosed in detail in U.S. Provisional PatentApplication Ser. No. 60/496,550, entitled “Table Saws with SafetySystems and Blade Retraction,” filed Aug. 20, 2003, the disclosure ofwhich is hereby incorporated by reference.

Shaft 242 extends outwardly from the right side of the arbor block asufficient distance so that a brake cartridge 252 may be pivotallymounted on the shaft, as shown in FIG. 30. The brake cartridge is sizedand positioned so that it is adjacent the perimeter of a blade having aspecified nominal diameter. The brake cartridge includes a pawl, and thepawl pivots toward the blade around shaft 242 to stop the blade fromspinning when the detection subsystem detects that a person hascontacted the blade, as described above. The brake cartridge may beconstructed and mounted in the saw in many ways. Examples of how thebrake cartridge may be constructed and mounted in a saw are disclosed inU.S. Provisional Patent Application Ser. No. 60/496,574, entitled “BrakeCartridges for Power Equipment,” filed Aug. 20, 2003, and U.S.Provisional Patent Application Ser. No. 60/533,575, entitled “BrakeCartridges and Mounting Systems for Brake Cartridges,” the disclosuresof which are hereby incorporated by reference. That provisional patentapplication also discloses how the position of the brake cartridgerelative to the perimeter of the blade may be adjusted by a linkagebetween the arbor block and the mounting structure for the brakecartridge. Arbor block 240 includes an aperture 253 through which a boltmay extend to adjust the spacing between the brake cartridge and theblade.

Brake cartridge 252 also acts as a mechanism to prevent a user of thesaw from installing a blade larger than recommended. The brake cartridgephysically blocks a large blade from being mounted on the arbor becausethe blade bumps into the brake cartridge.

Arbor 252 includes a pin 254 (labeled in FIG. 32) that engages an arborblock support mechanism 256 to hold the arbor block up and prevent thearbor block from pivoting around shaft 242 during normal operation ofthe saw. Pin 254 and arbor block support mechanism 256 also providerigidity to the arbor block and minimize any vibration of the arborblock during normal operation of the saw. However, when a personaccidentally contacts the blade the brake cartridge will engage and stopthe blade. The angular momentum of the blade as it is stopped willcreate a significant downward force and that force will cause pin 254 todisengage from the arbor block support mechanism. When the pin hasdisengaged, the arbor block will be free to pivot around shaft 242, sothe downward force resulting from stopping the blade will cause thearbor block to pivot down very quickly. The blade will also pivot downbecause the blade is supported by the arbor block. In this manner, theblade will retract below the tabletop of the saw when a personaccidentally contacts the blade.

The arbor block support mechanism is shown in detail in FIGS. 28 and 33through 36. An L-shaped bracket 260 is bolted onto surface 262 on theelevation plate (surface 262 is labeled in FIG. 43). The L-shapedbracket includes a projection 264 having a first surface 266 and asecond surface 268. The first and second surfaces define a corner region270 into which pin 254 would normally nest. Material from projection 264may be removed in the corner region to allow pin 254 to contact firstand second surfaces 266 and 268 at points that are somewhat distant fromeach other to better hold the pin. A small pivot arm 272 is mounted onL-bracket 260 so that the pivot arm may pivot around a bolt 274. Thepivot arm includes a tab 276 having a support surface 278. Supportsurface 278 also abuts against pin 254 to help hold the pin in placeduring normal operation of the saw. Pivot arm 272 also includes a distalend 280 shaped to include an aperture through which a shoulder bolt 282may pass. The shoulder bolt passes through distal end 280 and threadsinto projection 264 in the L-shaped bracket. A spring 284 and washer 286are positioned between the head of bolt 282 and distal end 280 of thepivot arm. The spring is sized to bias the pivot arm toward projection264. Thus, pin 254 is held in corner 270 by spring 284 pushing pivot arm272 against the pin. Threading bolt 282 into or out of projection 264will adjust the force exerted by spring 284 against pin 254.

When brake cartridge 252 stops the blade, the downward force caused bythe angular momentum of the blade will overcome the force of spring 284,and pin 254 will then push pivot arm 272 aside and move down. Projection264 includes a third surface 288 that connects with but slopes away fromsecond surface 268. Third surface 288 slopes away in order to provideclearance for pin 254 to move down. As soon as pin 254 moves down pastthe point where the third and second surfaces connect, the pin no longercontacts projection 264 so it is free to move down. Similarly, tab 276on pivot arm 272 is rounded to quickly release pin 254 when the pinbegins to move down. The intersection of second surface 268 with thirdsurfaces 288 is positioned substantially opposite the tangent point ofthe rounded tab 276 so that pin 254 is released from both projection 264and tab 276 substantially simultaneously.

A bumper or pad 290 is mounted on trunnion brace 134 below arbor block240, as shown in FIGS. 5 and 14. When the arbor block retracts, bumper290 stops the downward motion of the arbor block and helps absorb theenergy of the retraction. The arbor block includes a surface 292configured to contact bumper 290, as shown in FIGS. 31 and 32.

The energy of retraction may be significant. Accordingly, bumper 290 maybe selected from materials that have good dampening characteristics andarbor block 240 may be made from a ductile iron so that the arbor blockit is less likely to be damaged during retraction. Additionally,trunnion brace 134 should be constructed so that it is sufficientlystrong to support bumper 290 and withstand the force of impact with thearbor block.

Trunnion brace 134 and elevation plate 170 are both constructed toprovide clearance for the arbor block and blade to retract in case of anaccident. As shown in FIGS. 14 and 16, the trunnion brace sweeps downfrom front trunnion 126 to rear trunnion 128 so that the bottom of theblade will not contact the trunnion brace when the blade is fullyretracted. Elevation plate 170 also includes a recessed area 294(labeled in FIG. 22) that allows the arbor block to pivot down.

Saw 100 is powered by a motor 300 mounted to the bottom of elevationplate 170. The motor may be mounted to the elevation plate in many ways.In the depicted embodiment, tabs 302 projects up from the motor andsandwich a projection 304 on the bottom of the elevation plate(projection 304 is labeled in FIGS. 42 and 43). Bolts 305 and 306 passthrough holes in the tabs and projection to mount the motor to theelevation plate, as shown in FIGS. 10 and 11.

A drive shaft 310 extends from the motor and a pulley 312 is mounted onthe drive shaft. A double pulley 314 is mounted on the left end of shaft242 so that a first belt (not shown) may extend around the motor pulleyand the outside of the double pulley. A third pulley 316 is mounted onthe left end of arbor 251 and a second belt (not shown) extends aroundpulley 316 and the inside of double pulley 314. Motor 300 turns pulley312, which then turns double pulley 314 and arbor pulley 316, causingthe blade mounted on the arbor to spin. The depicted embodiment includesa double belt system as described so that arbor block 240 may retract bypivoting down around shaft 242 without disengaging from the drive belts.

Pulleys 314 and 316 are fixed-center pulleys, so a slightly stretchyPoly-V belt designed for fixed center pulleys is used. A slightlystretchy belt also has the advantage of being able to stretch and slipon pulley 316 when the brake cartridge stops the blade. This isadvantageous because pulley 316 will stop very suddenly when the brakecartridge stops the blade, but the motor and belts will continuespinning for a short period of time. A stretchy belt will be able tostretch and slip on pulley 316 when the pulley stops suddenly. Ofcourse, other belt and pulley configurations and belt tensioning systemsmay be used.

The belt around pulley 316 is preferably made of a static dissipativematerial so that static charge does not build up on the arbor or blade.This is advantageous because in some implementations a static charge mayinterfere with the detection subsystem. A standard belt or a slightlystretchy belt may extend around motor pulley 312 and the outside ofdouble pulley 314. The pulleys may be sized so that the blade spins at adesired speed, such as 4000 rpm, while the motor spins at a differentspeed, such as 3450 rpm.

The belt extending around the motor pulley and the outside of doublepulley 314 may be tensioned by moving the motor out. In the depictedembodiment, motor 300 is mounted to the elevation plate so that it maypivot around bolt 305. Tabs 302 include an oversized hole 308 throughwhich bolt 306 passes so that the motor may pivot around bolt 305. Toput tension on the belt, bolt 306 is loosened and the motor is pivotedaround bolt 305 away from the double pulley. When the desired tension isachieved, bolt 306 is tightened to hold the motor in position.

Trunnion brace 134 is shaped to partially shroud the blade under table102. Shrouding the blade prevents a person from contacting the bladeunder the table. This is useful because if a person contacts the bladeunder the table, the brake cartridge will fire and the blade willretract, possibly into the person's hand. Shrouding the blade also helpsto collect sawdust created when the saw is running.

Trunnion brace 134 is shaped to create a trough or channel 320, shown inFIG. 15. The trough is wide enough to shroud the blade and to allow aperson to reach into the saw through opening 106 in the tabletop tochange either the blade or brake cartridge. Trough 320 is sloped down,as shown in FIGS. 14 and 16, to direct sawdust toward a port 322 in thebottom of the trough. Preferably, the inside surface of the trough,including the bottom and side walls, is as smooth as possible to avoidtrapping sawdust. A hose coupling 324 is mounted to the bottom of thetrunnion brace over port 322. The coupling includes a mesh 326 sized toprevent the bolt and washer with which the blade is secured to the arborfrom falling through the mesh. It is possible when a user changes theblade that the blade nut or washer could fall into the saw and becomedifficult to retrieve. Mesh 326 prevents the bolt or washer from fallingwhere they would be difficult to retrieve. A flexible vacuum hose orother conduit (not shown) is connected to the bottom of the coupling andextends to a similar port on the back of the saw. Thus, sawdust iscollected by the blade shroud and then directed out through port 322 andthrough a conduit to the back of the saw. A user may connect a vacuumsystem to the port on the back of the saw to collect the sawdust and tocreate an airflow from the blade shroud to the back of the saw. The hoseor conduit between coupling 324 and the port on the back of the saw isflexible so it can move when the trunnion brace tilts.

A side blade shroud 330, shown in FIGS. 4, 8, 10 and 12, is mounted ontrunnion brace 134 to the right of the blade. This shroud furtherencloses the blade to prevent inadvertent contact with the blade and tocollect sawdust. Side shroud 330 is mounted to the trunnion brace by avertical hinge 332. The vertical hinge allows the side shroud to pivotout, away from the blade, around the vertical axis of the hinge.Pivoting the side blade shroud out provides additional room to changethe blade or brake cartridge. The additional room is especiallynecessary to slide brake cartridge off of shaft 242. The side shroudincludes magnets 333 to engage the rear trunnion and hold the sideshroud closed, although other mechanisms may be used to hold the sideshroud closed. The top of the side shroud is shaped and positionedsufficiently away from the underside of the tabletop so that the bladecan tilt to the left without the side shroud bumping into the undersideof the table.

A front shroud 340 is also mounted on the trunnion brace to the front ofthe blade. This shroud further helps enclose the blade and directsawdust to the port in the bottom of the trunnion brace. The right sideof this shroud is shorter than the left side in order to allow the bladeand trunnion brace to tilt to the left. This shroud would typically bemade of a lightweight material to reduce the weight of the saw.Alternatively, the trunnion brace itself may be designed to extend upand form the front blade shroud.

The underside of table 102 may include recesses to allow the blade torise to a predetermined height without the arbor block bumping into theunderside of the table.

The cabinet of the table saw may include in opening to allow access tothe internal mechanism of the saw. FIG. 3 shows saw 100 with a cover 342over such an opening. The cover is mounted to the cabinet with hinges soit can pivot open. A standard latch is used to keep the cover closed.The cover may include louvers to allow airflow into the cabinet.

Saw 100 may also include a switch box 344 with one or more switches tocontrol the operation of the saw. A switch box designed for use withsafety systems as described above is described in detail in U.S.Provisional Patent Application Ser. No. 60/533,598, entitled “Switch Boxfor Power Tools with Safety Systems,” the disclosure of which is herebyincorporated by reference.

Saw 100 may also come with a fence 346 that rests on table 102 andclamps to a front rail. The fence provides a face against which a usermay slide a work piece when making a cut. One possible fence isdisclosed in U.S. Provisional Patent Application Ser. No. 60/533,852,entitled “Improved Fence for Table Saws,” the disclosure of which ishereby incorporated by reference. The saw may also come with a mitergauge 348 and a blade wrench 350.

FIG. 44 shows a table saw with a riving knife 400 positioned adjacentthe back edge of the blade. FIGS. 45 and 46 show riving knife 400 in thesaw with the cabinet removed, and FIG. 47 shows the riving knife mountedin the saw with the table removed. The riving knife is shown alone inFIGS. 48 and 49.

Riving knife 400 is a flat, fin-like plate positioned in the sawadjacent the back edge of the blade. The riving knife is mounted in thesaw within the projected kerf and top-to-bottom cutting capacity of theblade. Thus, as a workpiece is cut by the blade, the riving knife willfit into the newly cut slot in the workpiece so that it does not blockor impede the movement of the workpiece past the blade.

Riving knife 400 functions to prevent a workpiece from engaging theteeth at the back of the blade. As a workpiece is cut into two sections,the newly cut sections may flex or move. If one of the newly cutsections moves to the side and catches the back edge of the spinningblade, the blade may suddenly kick the workpiece back toward the user ata very high speed and the user's hand may be pulled into the blade bythe sudden movement of the workpiece. The riving knife impedes theworkpiece from moving to the side and thereby minimizes the chance ofthe workpiece catching the back edge of the blade. The riving knife alsominimizes the chance of newly cut sections of a workpiece movingtogether and binding the blade.

As shown in FIGS. 48 and 49, the riving knife is flat, smooth andplanar. The sides of the riving knife are parallel and the riving knifehas a body thickness thinner than the kerf of the blade for which it isintended to be used. The body thickness, however, should not besubstantially thinner than the kerf of the blade or the riving knifewill be less able to impede a workpiece from catching the back edge ofthe blade. Typically, the riving knife has a body thickness thicker thanthe body thickness of the blade but thinner than the kerf of the blade.

The riving knife includes a leading edge 402 that is curved to followthe edge of whatever blade or blades are intended to be used with theriving knife. Leading edge 402 includes a chamfer 404 so that the edgedoes not catch on a workpiece as the workpiece is moved past the blade.The riving knife also includes a tip 406 rounded and chamfered so thatit does not catch on a workpiece. The rounded tip often has a radius ofnot less than 0.08 inch. The riving knife typically has a width ordimension from leading edge 402 to a back edge 408 of at least 116^(th)of the diameter of the smallest blade for which the riving knife isintended to be used, measured at the level of the table top when theriving knife is installed in a saw and raised to its maximum elevation.The riving knife may be made of steel with a hardness of between 38 HRCand 48 HRC and a resistance to rupture at least equal to 800 MPa. Theriving knife should be sufficiently rigid so as not to deflect ordisplace any significant distance toward the blade or to the side.

The riving knife is mounted in the saw close to the blade but nottouching the blade. The radial distance between the leading edge 402 andthe back of the blade is typically at least 0.11 inch (3 mm) but notmore than 0.31 inch (8 mm) at every point along the edge. The highestpoint of the riving knife is typically at least 0.04 inch (1 mm) but notmore than 0.20 inch (5 mm) below the highest point of the saw blade. Theriving knife is also mounted in the saw so that it remains in a fixedposition relative to the blade as the blade tilts and changes elevationrelative to the table. In other words, the riving knife tilts and movesup and down with the blade.

The riving knife may be used for most cuts performed on a table saw,including through-cuts (where the blade cuts through the entirethickness of the workpiece) and non-through-cuts (where the blade doesnot cut through the entire thickness of the workpiece). There are somecuts, however, where a riving knife may not be used, such as a plungecut where the blade is raised up into a workpiece and a cove cut wherethe workpiece is moved past the blade at an angle relative to the planeof the blade so that the blade removes a groove or cove of material. Inboth those cuts, the riving knife would be outside the cut produced bythe blade and would abut the workpiece. Additionally, a riving knifedesigned for a blade with a 10″ diameter should not be used with asmaller diameter blade because the riving knife would project above thecutting capacity of the blade. Similarly, dado blades (which are stacksof blades mounted on the saw to cut a groove in a workpiece) aretypically smaller in diameter than normal blades so riving knivesdesigned for normal blades would extend above the dado could not be usedbecause they would abut the workpiece. Dados are also substantiallythicker than normal blades and therefore a riving knife designed for asingle blade might not impede a workpiece from catching the back edge ofa dado stack.

It is desirable for a user to be able to install and remove the rivingknife quickly and easily when performing different operations with thesaw so that the riving knife is not an inconvenience. For example, if auser needs to make both non-through and dado cuts, then the user willhave to remove the riving knife before and re-install it after each dadocut. If it were complicated, difficult or time consuming to remove andreinstall the riving knife between the different cutting operations,then it would be less likely a person would use the riving knife.

The table saw shown in FIGS. 44 through 47 includes a mounting system ormechanism 410 that allows for fast and easy removal and reinstallationof riving knife 400. Mounting system 410 is shown isolated in FIGS. 50and 51.

Mounting system 410 includes a mounting plate 412 that is bolted ontoraised portion 250 of elevation plate 170 by bolts 414, as shown in FIG.47. Raised portion 250 is also shown in FIGS. 42 and 43. Mounting plate412 is shown isolated from other structure in FIGS. 54 and 55. Mountingplate 412 includes a flat bottom surface 415 that rests on raisedportion 250 of the elevation plate. Two holes 416 pass through themounting plate and bolts 414 extend through those holes and are threadedinto corresponding holes on raised portion 250. Holes 416 are oversizedrelative to bolts 414 so that the position of the mounting plate may beadjusted relative to the elevation plate. By adjusting the position ofthe mounting plate, the position of the riving knife relative to theblade may be adjusted, as will be explained below. Mounting plate 412also includes a flat face 418 and two holes 420 that pass through theface.

A positioning plate 422 is bolted onto face 418 of mounting plate 412 bybolts 424 that pass through holes 420 and are received into threadedholes 426. Holes 420 are oversized and oval shaped so that the positionof plate 422 may be adjusted. Positioning plate 422 is shown isolated inFIGS. 56 through 58. Positioning plate 422 functions to position theriving knife in the mounting system. The positioning plate includes aflat surface 428 to support one side of the riving knife and two pins430 that extend out from that flat surface, as shown. The base of rivingknife 400 includes two holes 432 and pins 430 are configured to extendthrough those holes to locate the riving knife in the mounting system.The positioning plate also includes two flanges 434 extendingperpendicularly out from opposite edges of flat surface 428, and eachflange includes a shoulder 436. Riving knife 400 includes correspondingedges 438 and shoulders 440 configured to position the riving knifebetween flanges 434 and on shoulders 436 against the positioning plate,as shown in FIG. 70. Thus, the riving knife is positioned in themounting system by fitting on pins 430 between flanges 434 and onshoulders 436.

Mounting system 410 also includes a clamping plate 442 that works withpositioning plate 422 to clamp and hold the riving knife in position.Clamping plate 442 includes a flat surface 444 that supports the side ofthe riving knife opposite the side supported by the positioning plate.Flat surface 444 includes recesses 445 that provide clearance for pins430 and for contaminants like sawdust so that the clamping plate canabut against the riving knife evenly. The clamping plate also includesshoulders 446 and edges 448 that correspond to shoulders 436 and flanges434 on the positioning plate so that the clamping plate fits betweenflanges 434 as shown in FIG. 51.

Clamping plate 442 also includes a hole 450 through which a bolt 452passes. Bolt 452 is labeled in FIG. 53. Bolt 452 passes through hole 450and is threaded into a hole 454 in positioning plate 422 to looselyconnect the clamping plate to the positioning plate. A spring 456, shownin FIG. 53, is placed over bolt 452 and is at least partially containedin a first circular recess 458 in positioning plate 422 and in a secondcircular recess 460 in clamping plate 444. Spring 456 may be acompression spring, a wave compression spring or some other spring.Spring 456 biases clamping plate 442 away from positioning plate 422 tohelp open the clamp, as will be described below.

Clamping plate 442 also includes a first set of cam surfaces 462 and 463and a second set of cam surfaces 464 and 465. The cam surfaces arepositioned in a recess 466 that is concentric with hole 450 and the camsurfaces are arcuately spaced around the hole, as shown. Cam surfaces462 and 464 slope up from the bottom of recess 466 to where they joinwith cam surfaces 463 and 465, respectively. In the depicted embodiment,each of cam surfaces 462 and 464 is a portion of a helix or coil with apitch of 50.5 mm. Each of cam surfaces 463 and 464 is a portion of ahelix or coil with a pitch of 1.01 mm. Of course, other cam surfaces andpitches may be used. The cam surfaces are used to move clamping plate442 toward positioning plate 422, as will be explained.

Mounting system 410 also includes a cam bushing 470 (shown isolated inFIGS. 62 through 65) configured to fit into recess 466 in the clampingplate. Cam bushing 470 includes cam surfaces 472 and 473 joined by afirst edge 471, and a second set of cam surfaces 474 and 475 joined by asecond edge 476. Those cam surfaces are arcuately spaced around a hole480, as shown, and they are configured to correspond roughly with thecam surfaces in the clamping plate. In the depicted embodiment, each ofcam surfaces 472 and 474 is a portion of a helix or coil with a pitch of44 mm. Each of cam surfaces 473 and 475 is a flat surface. Other camsurfaces and pitches may be used. Cam bushing 470 also includes a flange478 to abut against the front of the clamping plate to limit thedistance the bushing may extend into recess 466.

Cam bushing 470 has an octagon-shaped drive head 482 that can be grippedto turn the bushing and a 12-point inner socket 484 positioned in drivehead 482, as shown in FIG. 62. Bolt 452 passes through hole 480 in thecam bushing and through hole 450 in the clamping plate and then screwsinto hole 454 in the positioning plate, as shown in FIG. 53. The head ofbolt 452 may then fit into 12-point inner socket 484.

Mounting system 410 also includes a handle 490, shown in FIGS. 66through 68. Handle 490 has an elongate body with an 8-facet socket 492at one end configured to fit over octagon-shaped drive head 482 on cambushing 470. A set screw is threaded into a hole 494 on the handle tohold the handle and the cam bushing together when socket 492 ispositioned over drive head 482.

The various components of mounting system 410 described above may bemade from various strong and hard materials, such as machined metal,powder metal or cast metal. It is also possible that the components caybe made from a hard plastic or thermoset. The materials of the cambushing and clamping plate may be selected to facilitate the sliding ofthe cam surfaces and to minimize galling, and/or the cam surfaces may belubricated or greased. The cam bushing and handle may be combined intoone single part.

Mounting system 410 may be thought of as having an open position wherethe clamping and positioning plates are spaced apart from each other anda closed position where the two plates are moved closer together. Theopen position is shown in FIGS. 71 and 72. In that position, handle 490is raised and plates 422 and 442 are spaced apart. The mounting systemshould be configured and adjusted so that in the open position plates422 and 442 are spaced sufficiently far apart for the riving knife to bemoved off of pins 430 and removed from between the plates. The closedposition is shown in FIGS. 50, 51 and 69. In that position handle 490 islowered and plates 422 and 442 are closer together to clamp the rivingknife and hold it in position.

When handle 490 is moved up to open the clamp, the handle turns cambushing 470 so that the cam bushing fits into recess 466 on the clampingplate without engaging the cam surfaces. In that position, spring 456pushes the clamping plate and cam bushing away from positioning plate422 until the cam bushing abuts the head of bolt 452 and the clampingplate abuts the cam bushing. The distance the clamping plate may moveaway from the positioning plate can be adjusted by turning bolt 452.Threading bolt 452 into hole 454 on the positioning plate lessens thedistance the clamping plate may move out because it moves the bolt headand cam bushing closer to the clamping plate. Threading the bolt out ofhole 454 increases the distance the clamping plate may move out. Bolt452 may be threaded in or out by pressing the clamping and positioningplates together and pressing the cam bushing into recess 466. The headof bolt 452 will then extend out beyond the cam bushing so that it maybe gripped and turned by hand or with a wrench. When the bolt isadjusted to its desired position, the cam bushing and plates arereleased and spring 456 pushes them out until the cam bushing abuts thehead of the bolt and the bolt head fits into socket 484 in the cambushing. Socket 484 is a 12-point socket so that the bolt head can fitinto the socket in many different positions and thereby allow fineadjustment of the distance bolt 452 is threaded into hole 454. Spring456 is sized and selected so that it is at least partially compressedeven when the mounting system is in the open position. For example, thespring may be sized and selected so that it applies 5 to 15 pounds offorce against the clamping plate in the open position, and more forcewhen compressed. In this manner, the spring biases the clamping plateout so that the mounting system opens when handle 490 is raised.

With mounting system 410 in the open position, riving knife 400 may beplaced in the clamp with holes 432 in the riving knife fitting aroundpins 430 on the positioning plate and shoulders 440 on the riving kniferesting on shoulders 436 of the positioning plate, as shown in FIG. 70.In this manner, the riving knife is positioned in the mounting system.The base of the riving knife includes a cut-out 502 to provide clearancefor bolt 452 and spring 456.

Handle 490 may then be moved down to clamp the riving knife between thepositioning and clamping plates. Moving handle 490 down causes cambushing 470 to turn. When the cam bushing turns, cam surfaces 472 and474 and/or leading edges 471 and 476 slide up cam surfaces 462 and 464,respectively, on the clamping plate and push the clamping plate towardthe positioning plate. The cam surfaces and/or edges push the clampingplate toward the positioning plate because the cam surfaces are inclinedand because bolt 452 prevents the cam bushing from moving out. The camsurfaces are inclined somewhat steeply so that a relatively smallrotation of the handle will cause a significant movement of the clampingplate toward the positioning plate. For example, the cam surfaces may beconfigured to move the clamping plate toward the positioning plate3/16ths of an inch by moving the handle through only 20-40 degrees ofarc. Of course, other configurations and geometries are possible.

When edges 471 and 476 move to the top of cam surfaces 462 and 464, camsurfaces 473 and 475 on the cam bushing will engage cam surfaces 463 and465 on the clamping plate. Continued downward rotation of the handlewill then cause cam surfaces 473 and 475 to slide over cam surfaces 463and 465. These cam surfaces are configured and sized so that when theyengage, the cam bushing and clamping plate are stable, with little or noforce tending to move the cam surfaces to unclamp the mounting system.In other words, the geometry of the cam surfaces prevents vibration orother factors from causing the mounting system to unclamp or open. Onepossible configuration is to make cam surfaces 463, 465, 473 and 475relatively flat and smooth with only very little or no slope. Of course,numerous configurations of the cam surfaces are possible and variousslopes and shapes may be used depending on the desired movement andclamping action.

As handle 490 rotates down, bolt 452 will unthread from hole 545 andthereby loosen the clamping action. This loosening is not particularlynoticeable as cam surfaces 472 and 474 and/or leading edges 471 and 476slide up cam surfaces 462 and 464 because the cam surfaces move theclamping plate much more than the bolt loosens due to the fact that thepitch of the cam surfaces is much greater than the pitch of the threadson the bolt. However, as cam surfaces 473 and 475 slid over cam surfaces463 and 465 the loosening of the bolt is more noticeable because thosecam surfaces typically do not have a significant pitch. Accordingly, camsurfaces 463 and 465, and/or cam surfaces 473 and 475, may be inclinedslightly to match the pitch of the threads on the bolt so that the camsurfaces tighten the clamp in the same amount as the unthreading boltloosens the clamp. Alternatively, one set of cam surfaces may have apitch slightly greater than the pitch of the threads on the bolt and theother set of cam surfaces may be flat. This is the configuration shownin the depicted embodiment, where the pitch of the threads on bolt 452is 1 mm, the pitch of cam surfaces 463 and 465 is 1.01 mm, and camsurfaces 473 and 475 are flat. This configuration tightens the clampslightly more than the unthreading bolt loosens the clamp. As anotheralternative, those cam surfaces may incline slightly less than the pitchof the threads on the bolt so that the clamping action is slightly lessthan the loosening of the clamp by the unthreading of the bolt. In thatconfiguration, the downward movement of the handle becomes slightlyeasier as the bolt unthreads. This configuration also creates what maybe thought of as a slight hump or “detent” that must be overcome whenhandle 490 is raised to open the clamp, and that hump helps prevent anyunintentional opening of the clamp.

Handle 490 also includes a shoulder 496 (shown in FIGS. 66 and 67), andclamping plate 442 includes a boss 500 (shown in FIGS. 60 and 61)adapted to receive a bolt 498 (shown in FIGS. 51 and 52). Shoulder 496on the handle is adapted to abut against bolt 498 as the handle rotatesdownward so that bolt acts as a stop to limit the rotation of thehandle. Without that stop, the handle could rotate downward until thecam bushing could again fit into recess 466 and thereby allow the clampto open. Numerous other stops are possible, including a stop integralwith the clamping plate.

When included in a saw, mounting system 410 is accessible to a user ofthe saw through opening 106 in the table, as shown in FIG. 73.Typically, a throat plate or table insert 510 would be positioned inopening 106, as shown in FIGS. 44 and 46. A user would simply remove thethroat plate, reach through the opening, grasp handle 490, and move itup or down as required to install or remove the riving knife.Specifically, to install the riving knife a user would simply movehandle 490 up to open the mounting system, place the riving knife on thepositioning plate, and then move the handle down to clamp the rivingknife in place. Handle 490 includes a bend or step 506, labeled in FIG.68, to move the handle out and away from other components in the saw sothat the handle is easy to grasp. Handle 490 may be sized so that it islong enough to extend up through opening 106 and above the tabletop whenthe mounting system is in the open position with the handle raised, evenwhen the blade is set to its lowest elevation. By so doing, a user wouldbe reminded before using the saw that the riving knife was not clampedinto position because the handle would interfere with the throat plate.The geometry of the handle and mounting system may also be configured sothat when the handle is moved up, it remains up without falling backdown due to gravity.

Mounting system 410 may be adjusted to accommodate riving knives ofvarious thicknesses by adjusting bolt 452, as explained. Threading bolt452 in or out also adjusts the amount of force applied during clamping.

Mounting system 410 is adapted so that the position of the riving kniferelative to the blade may be adjusted. The side-to-side andfront-to-back position of the riving knife, as well as the twisting oryaw of the riving knife relative to the blade, may be adjusted to makesure the riving knife is within the kerf of the blade and within thedesired radial distance from the back edge of the blade by looseningbolts 414, moving the mounting system as necessary, and thenre-tightening the bolts. The elevation or height of the riving kniferelative to the blade may be adjusted by loosening bolts 424, movingpositioning plate 422 up or down as necessary, and then re-tighteningthe bolts. The angle or slope of the riving knife toward or away fromthe back edge of the blade also may be adjusted by loosening bolts 424and pivoting positioning plate 422 toward or away from the blade,although the amount plate 422 can pivot will depend on the size of holes420 in mounting bracket 412 and on the size of bolts 424.

Once the position of the mounting system relative to the blade has beenset, the riving knife may be removed and re-installed repeatedly withouthaving to re-adjust the position of the riving knife. The riving knifewill fit onto positioning plate 422 and the clamping action of themounting system will press the riving knife against surface 428 of onthe positioning plate, thereby locating the riving knife in the sameposition each time it is re-installed into the mounting system. A usermay therefore remove the riving knife when necessary for a givenoperation and replace the riving knife quickly and easily without toolsand without having to re-adjust the position of the riving knife. Theability of the mounting system to position the riving knife accuratelywhen it is re-installed may be thought of as indexing the riving knifeto a predetermined position.

As stated above, mounting system 410 is mounted on portion 250 ofelevation plate 170. Mounting the mounting system on the elevation platemeans that the mounting system and riving knife will move up and downand tilt with the blade as the blade moves. Thus, the position of theriving knife relative to the blade remains constant as the position ofthe blade relative to the table changes.

Mounting system 410 is constructed so that items other than a rivingknife may be attached to or mounted in the saw. Any item that includes abase configured to fit over positioning plate 422 and sized to beclamped between the positioning plate and clamping plate 442 may bemounted and indexed in the saw as described.

Blade guard assembly 108 is another item that may be mounted and indexedin mounting system 410. Blade guard 108 is shown isolated in FIGS. 74through 81. Blade guard 108 includes a blade shroud 520 shaped to fitover the blade and shield a person from accidentally contacting theblade. The shroud forms a cavity in which the blade may spin. The shroudis made from a nonconductive material such as polycarbonate or someother plastic so that the shroud will not affect any electrical signalon the blade if the shroud comes into contact with the blade and if thesaw includes a contact detection system as described above. (In fact,blade guard 108 is constructed so that no metal or conductive part ofthe guard can contact the blade.) The material of the shroud should besufficiently soft so that it will be unlikely to damage the blade if theshroud comes into contact with the blade. Often shroud 520 is made of aclear plastic so that the blade can be seen through the shroud andespecially so that the cutting edge of the blade can be seen through theshroud by an operator of the saw. Shroud 520 is made from two halvesjoined together by screws, nuts and bolts, sonic welding, adhesive,clips or some other method or it can be a single molded piece.

The bottom of each side of blade shroud 520 includes a flat edge 522adapted to rest on tabletop 102 when the blade is set at 90-degreesrelative to the table top. Alternatively, the bottom edge of one sidemay be raised slightly to accommodate when the blade tilts relative tothe tabletop. The left bottom edge when facing the saw in the normaloperating position would be raised for a left-tilting saw and the rightbottom edge would be raised for a right-tilting saw. In thisconfiguration, if one bottom edge rests on the tabletop when the bladeis set at 90-degrees, the other bottom edge typically would rest on thetabletop when the blade is tilted to 45-degrees.

Blade shroud 520 also includes a top edge 524 shaped to curve closelyaround the blade. The spacing between the perimeter of the blade when itis fully elevated and the inside surface of the blade shroud at theclosest point can be approximately ¼ to ½ inch, for example, althoughother spacings are possible. The top edge of the blade shroud followsclosely to the curve of the blade when the blade is fully elevated inorder to minimize the size of the shroud, to create a substantiallysmooth and curved inside surface for dust collection, and to present apleasing appearance.

A front portion 526 of the blade shroud extends up and out from theshroud, as shown, and may be thought of as a horn. Front portion 526extends up to provide a contact surface for a workpiece to abut as theworkpiece moves toward the blade. When the workpiece abuts the frontportion, the workpiece will push the guard up to allow the workpiece toslide under the guard and past the blade. Front portion 526 is sized toaccommodate the maximum cutting depth of the saw, which, for example, isoften 3.125 inches. In other words, front portion 526 is sized so thatthe thickest workpiece that can be cut on the saw will abut the surfaceand push the guard up. The front portion is angled so that the workpiecewill not catch on the shroud when the workpiece moves toward the blade.A wall or barrier 527 (labeled in FIG. 79) may be molded into the shroudbetween the main inside cavity of the shroud and the front portion sothat sawdust does not collect in the front portion.

Bottom edges 522 of the blade shroud also include inwardly projectingflanges 532, one on each side, as shown in FIGS. 79 and 80, that addstrength to the shroud. (FIG. 80 shows a front view of the blade guard).Flanges 532 also will abut the blade if the shroud deflects to the side,thereby protecting the shroud from the blade by minimizing the regionover which the blade contacts the shroud.

Blade shroud 520 is also configured to fit closely to the sides of theblade, as shown in FIGS. 78 and 79 which show top and bottom views,respectively, of blade guard 108 and blade shroud 520. A right side 528and a left side 530 of the blade shroud are shown in those figures. Theinside spacing between those sides can vary from approximately ¼ inch atthe closest point to approximately ¾ or 1 inch at the widest point. Thefront of the blade shroud has a wider dimension than the rear becausethe blade shroud will have more play or side-to-side movement at thefront than at the rear, as will be explained.

The right side of the blade shroud is configured as close to the bladeas possible so that the fence of the table saw can be moved as close aspossible to the blade before bumping into the guard. The right side ofthe blade shroud is flatter than the left side, as shown in FIG. 78,because the fence is typically used on the right side of the blade.Configuring the shroud to be close to the sides of the blade, andparticularly close to the right side of the blade, allows the guard tobe used when the fence must be positioned close to the blade.

The configuration of blade shroud 520 described herein may be thought ofas a low-profile configuration because the shroud fits closely aroundthe blade. This low-profile configuration reduces the degree that theblade guard interferes with the operation of the saw and is lessobtrusive than other guards. Making the blade guard and blade shroud assmall and unobtrusive as possible increases the likelihood that theguard will be used and will not be removed by a user of the saw. Thelow-profile guard also minimizes the regions in which sawdust maycollect and directs sawdust to a collection area below the tabletop ofthe saw.

Blade shroud 520 is pivotally connected to a support arm 536. Supportarm 536 is a folded metal arm with a U-shaped cross section, and isshown isolated in FIG. 82. Support arm 536 includes a first tab 538 witha first hole 540 and a second tab 542 with a second hole 544. Tabs 538and 542 are adapted to fit over and around a designated portion of bladeshroud 520. Specifically, blade shroud 520 includes a hole 546 near thetop edge of the shroud (as shown in FIG. 84) and support arm 536 isadapted to fit over the shroud so that holes 540 and 544 in the supportarm align with hole 546 in the shroud. Hole 546 extends through a bossthat spans the shroud from one side to the other. A steel pin 548extends through the holes to pivotally connect the blade shroud to thesupport arm.

Pin 548 is shown in FIG. 86. Pin 548 includes a main section 550 that islightly press fit into hole 546 in the blade shroud so that the pin isheld snug and securely by the blade shroud so that there is no playbetween the blade shroud and the pin. Main section 550 of the pin has adiameter sized to fit securely into second hole 544 in the support armso that the pin can rotate in the hole with very little play. The end ofpin 548 that fits into hole 544 is substantially flush with the outsidesurface of the support arm when the pin is positioned properly so as notto increase the side-to-side dimension of the overall blade guard.

Pin 548 also includes a first recessed section 552 and a second recessedsection 554. The change in diameter from main section 550 to firstrecessed section 552 creates a shoulder 555 that abuts against theinside surface of tab 538 on the support arm. The diameter of hole 540in tab 538 is sized to accept first recessed portion 552 so that the pincan rotate in the hole with very little play, but the diameter of hole540 is smaller than the diameter of main section 550. In this manner,the position of shoulder 555 defines the position of the pin in holes540 and 544. The length of main section 550 is substantially equal tothe distance between the inside surface of tab 540 and the outsidesurface of tab 542. Second recessed portion 554 is configured to receivea clip 556 to hold the pin in place. FIG. 87 shows clip 556 on pin 548,and FIGS. 87 and 88 both show the pivot connection between blade shroud520 and support arm 536.

The pivot connection between blade shroud 520 and support arm 536 allowsfor a metal-to-metal pivot rather than a metal-to-plastic pivot becausetabs 538 and 542 in the support arm contact pivot pin 548. Having ametal-to-metal pivot connection permits the connection to be moreprecise than it otherwise could be because the metal components may bemanufactured with smaller or tighter tolerances and because themetal-to-metal pivot connection will wear less than other connections.This is important because a more precise pivot connection means therewill be less play, vibration or side-to-side movement of the bladeguard.

Support arm 536 is also designed to have a significant width orside-to-side dimension between tabs 538 and 542. That width providesstability for the blade shroud and minimizes the play, vibration, andside-to-side movement that could otherwise result. One possible width orside-to-side dimension of support arm 536 is around 1.5 inches, althoughother dimensions are possible. Making support arm 536 relatively wide,however, means that the support arm is wider than the blade shroud.Accordingly, left side 530 of the blade shroud includes a raised portion560 so that the blade shroud fits and substantially fills the spacebetween tabs 538 and 542 on the support arm, as shown in FIGS. 79 and80. Raised portion 560 also includes flat outside surfaces to minimizeor eliminate any interference with the inside surfaces of tabs 538 and542 on the support arm when the blade shroud pivots around pin 548. Hole546 in the blade shroud passes through raised portion 560. Typically,there would be some minimal clearance between the inside surfaces of thesupport arm and the outside surfaces of the blade shroud so there is nofriction or drag between them when the shroud pivots. Alternatively, thesize of raised portion 560 and the resulting side-to-side dimension ofthe blade shroud can be selected to create a desired amount of frictionbetween the blade shroud and the support arm so that a predeterminedamount of force is required to pivot the blade shroud.

Tabs 538 and 542 on the support arm create an open region 562 thatprovides clearance for the blade shroud to pivot. Open region 562 islimited by edge 564 and upper surface 566. Blade shroud 520 includes aprojection 568 that acts as a stop to limit the counterclockwiserotation of the blade shroud when viewed as in FIG. 76. Projection 568includes a curved surface 570 and a tab 572 extends out from surface570. Projection 568 is sized so that curved surface 570 slides past edge564 in the support arm when the blade shroud pivots, but tab 572 abutsupper surface 566 on the support arm when a predetermined amount ofrotation has occurred.

The clockwise rotation of blade shroud 520 when the shroud is viewed asin FIG. 76 is limited by a flange 574 cut out of the upper surface ofsupport arm 536. Flange 574 is bent down toward the blade shroud, asshown in FIG. 82, so that the back of top edge 524 on the shroud willcontact the flange after the blade shroud has rotated a given amountrelative to the support arm.

The end of support arm 536 opposite tabs 538 and 542 is pivotallyconnected to a spreader or splitter 580. Splitter 580 is a flat, metalplate similar to the riving knife discussed above. The splitter has aside-to-side thickness thinner than the kerf of the blades for which itis intended to be used and the splitter is positioned in the saw behindand within the kerf of the blade, like the riving knife. The splitter,however, extends above the height of the fully elevated blade so that ablade shroud may be mounted thereto.

Splitter 580 includes a front edge 582 curved to follow the perimeter ofthe blades with which the splitter is to be used, like the leading edgeof the riving knife discussed above. The splitter also includes arounded tip 584 similar to the tip of a riving knife. Curved edge 582and tip 584 are chamfered so that they do not catch on a workpiece.Splitter 580 also includes an upper edge 586 extending up and away fromtip 584 and a portion of that upper edge is chamfered. Splitter 580includes a base 588 with shoulders, edges, holes and cutouts like thosein the riving knife discussed above so that the splitter may fit intomounting system 410, as shown in FIGS. 89 and 90.

Support arm 536 includes two side walls 590 and 592 (labeled in FIG. 82)and two holes 594 and 596 are cut in the side walls at the end of thesupport arm opposite tabs 538 and 542. A corresponding hole 598 ispositioned in splitter 580 toward the top and back of the splitter.Support arm 536 is positioned over the splitter so that hole 594 and 596align with hole 598. A nut 600 (shown in the assembly in FIG. 81 andisolated in FIG. 91) is positioned between the splitter and side wall592 of the support arm. Nut 600 includes a recessed section 602 with ashoulder 604. Recessed section 602 is sized to fit into hole 596 withoutany significant play. Recessed area 602 is also sized so that itpreferably does not extend through hole 596 beyond the outer surface ofwall 592 so as to minimize the overall width of the blade guardassembly. Shoulder 604 is sized larger than hole 596 so that theshoulder abuts the inside surface of wall 592. Nut 600 also includes athreaded hole 605 to receive a screw, as will be explained.

A spacer 606 (shown in FIGS. 81 and 92) is positioned between splitter580 and wall 590 of support arm 536. Spacer 606 includes a recessedsection 608 with a shoulder 610, and recessed area 608 is sized to fitinto hole 594 without any significant play. Recessed area 608 issufficiently long so that it extends through hole 594 and slightlybeyond the outer surface of wall 590. Shoulder 610 is sized larger thanhole 594 so that the shoulder abuts the inside surface of wall 590.Spacer 606 also includes a hole 612 through which a screw may pass.

A screw 614 (shown in FIG. 81) passes through a lock washer 616 and aflat washer 618 and then through spacer 606 and hole 598 in the splitterto thread into nut 600. As screw 614 threads into nut 600, the nut isdrawn against the splitter and the washer and lock washer are drawnagainst the end of spacer 606 that extends through hole 594. Thus,threading the screw into nut 600 causes the nut and spacer to clamp thesplitter around hole 598 and thereby pivotally mount the support arm onthe splitter.

The pivot connection between splitter 580 and support arm 536 is ametal-to-metal pivot, as with the pivot connection between blade shroud520 and support arm 536, because holes 594 and 596 in the support armcontact the recessed areas or shoulders on nut 600 and metal spacer 606.Having a metal-to-metal pivot connection permits the connection to bemore precise than it otherwise could be because the metal components maybe manufactured with smaller or tighter tolerances and because themetal-to-metal pivot connection will wear less than other connections.This is important because a more precise pivot connection means therewill be less play, vibration or side-to-side movement of the bladeguard.

Support arm 536 includes a cutout 620 to provide clearance for thesplitter when the support arm pivots up. The size of the cut out willdetermine how far upward the support arm can pivot. In the depictedembodiment, cutout 620 is sized to abut the top edge of the splitterwhen the support arm and blade shroud are pivoted up to a point wherethe center of mass of the support arm and blade shroud are behind hole598 (or to the right of hole 598 when the blade guard is viewed as inFIG. 93), regardless of the pivot position of the blade shroud relativeto the support arm. In that configuration, gravity will cause the bladeguard to stay up when a user pivots the guard to its uppermost limit, asshown in FIG. 93.

Blade shroud 520 includes a slot 622, shown in FIG. 85, extending alongthe back edge of the shroud from the bottom edge up toward the pivotconnection with the support arm. Slot 622 is positioned in theside-to-side center of the shroud. Slot 622 is configured so that whenthe blade shroud is lowered to cover the blade, the splitter fits intoslot 622, as shown in FIGS. 74 through 77 and FIG. 90. The width of theslot is sized so that the edges of the slot are close to the sides ofthe splitter. By having the splitter extend into the slot in the shroud,the splitter helps stabilize the shroud and prevents the shroud frommoving to the side. If the shroud starts to move to the side, an edge ofthe slot will abut splitter and stop that motion before the shroudcontacts the blade. The slot is long enough so that the splitter staysin the slot as the blade shroud pivots up to accommodate a workpiece.Slot 622 also includes an opening 624 at the bottom of the blade shroudthat includes angled or chamfered sides, as shown in FIGS. 79, 81 and85, to direct the splitter into the slot as the blade shroud is lowered.

With this configuration, the forward portion of the splitter may bethought of as supporting or stabilizing the guard or blade shroud. Thisconfiguration may also be thought of as having the splitter and bladeshroud interact to stabilize the back end of the shroud. Stabilizing theshroud with the splitter lets the shroud have a relatively smallside-to-side dimension at the back of the shroud.

In use, as a person feeds a workpiece toward the blade of the saw, theworkpiece will contact the blade guard and push the blade shroud up. Theblade shroud will pivot around pin 548 and the blade shroud and supportarm will move up by pivoting around screw 614. The blade shroud will bestabilized by the wide pivot connections and the splitter. The bladeshroud will move up until the workpiece can slide under and past theguard, at which time gravity will cause the shroud to move down and reston the tabletop. Additionally, support arm 536 and blade shroud 520 willpivot up and down relative to splitter 580 when the blade moves up anddown because the splitter is mounted in mounting system 410 and willtherefore move with the blade, as explained. For example, as the bladeand splitter move down, support arm 536 and blade shroud 520 will pivotup relative to the splitter because the blade shroud rests on thetabletop.

In the depicted embodiment, the vertical dimension of splitter 580 andthe position of hole 598 in the splitter are selected to positionsupport arm 536 so that the pivot point is approximately centered in therange of motion of the support arm. In other words, beginning with thesplitter fully elevated and then moving the splitter to its fullyretracted position, the support arm will pivot roughly the same amountsabove and below a horizontal position. Centering the pivot point in therange of motion of the pivot arm minimizes any front-to-back motion ofthe blade shroud as the splitter moves up and down. Of course, thesplitter may be configured to position the support arm differently. Thevertical dimension of splitter 580 and the position of hole 598 are alsoselected to be higher than the maximum cutting depth of the saw so thata thick workpiece can be slid past the splitter without bumping intosupport arm 536. The location where the support arm connects to theblade shroud in the depicted embodiment is chosen to minimize the lengthof the support arm while still holding the blade shroud in its desiredposition and while still providing stability to the blade shroud.Minimizing the length of the support arm minimizes the effect on theblade shroud of any play in the connection between the support arm andthe splitter. The position of flange 574 in the support arm and thedistance the flange extends down toward the blade shroud are selected sothat the flange is close to the top of the shroud when the splitter isfully retracted. The flange will prevent the blade shroud and supportarm from folding up, especially when a workpiece contacts the shroudwith the splitter retracted.

Stabilizing the back of the blade shroud with the splitter; securing theblade shroud to the support arm with a relatively wide, metal-to-metalpivot connection; and clamping the support arm to the splitter with arelatively wide, metal-to-metal pivot connection results in a bladeguard that is stable and that has little side-to-side play. Thisstability allows for a low-profile guard as described that interferesless with the operation of the saw, is less intrusive, and is morefunctional than other guards and therefore is more likely to be used.

In the depicted embodiment, the overall width or side-to-side dimensionof blade guard 108 is substantially defined by the width of support arm536, as shown in FIGS. 78 through 81, and blade shroud 520 is containedwithin that width. Screw heads and pins used in the depicted embodimentextend beyond the left side of the support arm rather than the right, tothe extent possible, so that the fence can be positioned as close aspossible to the right side of the guard.

Blade guard 108 can also include anti-kickback pawls 630, one pawlmounted to each side of splitter 580, as shown in FIGS. 74 through 77and FIG. 94. The anti-kickback pawls are mounted to the splitter by abolt 632 that extends through holes in the pawls, through spacers 634,and through a hole 636 in the splitter, as shown in FIG. 81. Bolt 632then screws into nut 638. Bolt 632 may be a flat head bolt or it may becountersunk if possible to minimize the distance it extends beyond theouter surface of support arm 536. Washers may be placed between the bolthead and pawl and between the nut and pawl. Spacers 634 may haveshoulders so that the bolt and nut tighten against the spacers and clampthe spacers to the splitter. The anti-kickback paws would then rest onthe shoulder of the spacers. A torsion spring 640 may be placed over thespacers and over the top of the splitter with an end connecting to eachof the two anti-kickback pawls, as shown in FIGS. 81 and 94. The torsionspring biases the pawls toward the tabletop of the saw. A spring pin 642is placed through a hole 644 in the splitter to limit the forwardmovement of the anti-kickback pawls. Each side of support arm 536includes a recess 645 to provide clearance for bolt 632, spacers 634 andspring 640.

When a user feeds a workpiece into the saw, the workpiece will move pastthe blade and contact the anti-kickback pawls and push them up so thatthe workpiece can continue to slide past the pawls. The anti-kickbackpawls are mounted to the splitter above the maximum cutting depth of thesaw so that the pawls do not block a workpiece.

The anti-kickback pawls are configured so that if a workpiece is pulledback or if a force tries to move the workpiece toward the front of thesaw, the anti-kickback pawls will resist that movement. Specifically,the anti-kickback pawls include teeth that are angled so a workpiece mayslide past the pawls toward the rear of the saw but the teeth will biteinto the workpiece if the workpiece moves toward the front of the saw.The pawls are also shaped so that they will bind against the workpiecewhen the workpiece moves toward the front of the saw. Each anti-kickbackpawl has a sufficient number of teeth so that at least one tooth willengage a workpiece regardless of the elevation of the splitter. Theteeth are configured so that their approach or bite angle remains around45 degrees and preferably around 60 degrees regardless of the elevationof the splitter.

The anti-kickback pawls in the depicted embodiment are positioned behindand outside the blade shroud rather than inside the blade shroud. Theblade shroud does not extend back over the anti-kickback pawls. Theanti-kickback pawls are also configured to be within the width orside-to-side dimension of support arm 536, as shown in FIG. 81. Thisconfiguration contributes to the blade guard having a low-profile and tothe blade shroud being at least partially stabilized by the leading edgeof the splitter, as explained.

The anti-kickback pawls are mounted on the splitter and therefore willmove up and down with the splitter. As the splitter moves up and down,the anti-kickback pawls will contact and slide on the tabletop or tableinsert. Thus, the tabletop or insert should have a surface toaccommodate the sliding of the teeth of the anti-kickback pawls thereon.In the depicted embodiment, the anti-kickback pawls are configured sothat they contact the insert only; they do not contact table 102.

A throat plate or table insert 510 is shown isolated in FIGS. 95 through97. Insert 510 is configured to fit in opening 106 in table 102 and theinsert is adapted for use with the detection and reaction systemsdescribed above, with mounting system 410, with riving knife 400 andwith blade guard 108.

Insert 510 is made from a non-conductive, hard material such as phenolicso that it does not affect or interfere with any electrical signal onthe blade. The insert may also be made from other hard, non-conductivematerials. If the insert were conductive, then contact with the bladewould likely ground out any signal on the blade and cause a reactionsystem to trigger. The insert can also be made from a relatively softermaterial such as nylon with a support plate or bracket molded in theinsert or otherwise associated therewith to give the insert rigidity.

Insert 510 includes a right portion 650 and a left portion 652, whichare separate pieces. Right portion 650 is shown individually in FIGS. 98through 100 and left portion 652 is shown by itself in FIGS. 101 through103. Typically a table insert for a table saw is a single piece, butinsert 510 is a two-piece insert to accommodate blade guard 108 andmounting system 410. For example, to mount blade guard 108 in mountingsystem 410 a user must remove the table insert to clamp the blade guardin position. However, with the blade guard clamped in position, aone-piece insert could not be placed in the table opening unless theinsert had a slot big enough to fit around or over the blade guard. Butif the insert had such a slot, then the insert would be weak and morelikely to break. Using a two-piece insert addresses this issue becauseonly one piece of the insert would need to be removed to install theblade guard; the other portion of the insert would remain in place. Inthe depicted embodiment, removing right portion 650 of insert 510 fromtable opening 106 provides sufficient clearance for the blade guard tobe mounted in the saw; left portion 652 of the insert need not beremoved. Right portion 650 can then be reinserted into the table openingafter the guard is mounted in the saw because right portion 650 does notwrap around the blade guard; it extends along one side of the guardonly.

A two-piece insert may take many different forms. In the depictedembodiment, right portion 650 and left portion 652 abut along a seam 654which extends from the front of the insert to a predetermined point downthe length of the insert. A slot 656 then extends from the terminus ofseam 654 to the rear of the insert, as shown. Slot 656 is not longenough to allow the blade to extend up through the insert, so a slotmust be cut in the insert to accommodate the blade when the insert isfirst placed in the saw. A slot is cut in the insert by lowering theblade below the tabletop, inserting and securing the insert in the tableopening, and then turning the saw on and raising the spinning bladethrough the insert.

An insert in which at least a portion of the blade slot is cut by theblade itself is called a zero-clearance insert because the insert comesclose to the sides of the blade with almost zero clearance. Azero-clearance insert has the advantage of supporting a workpiece closeto the blade to minimize any chipping of the workpiece that may occurduring cutting.

Slot 656 is pre-formed in insert 510 and the length of the slot may varydepending on how much of the slot is to be cut by the blade, if any.Slot 656, as shown in FIGS. 95 through 97, is long enough to allow auser to cut the slot with a riving knife installed in the saw becauseslot 656 is long enough to provide clearance for the riving knife as theblade rises up through the insert. Alternatively, slot 656 may beshortened so that the riving knife must be removed before the slot iscut. In that case, slot 656 could extend only far enough to allow ariving knife or blade guard to extend above the insert after the bladehas cut the slot in the insert. As still another alternative, slot 656could extend sufficiently far so that the blade need not cut a slot inthe insert at all. In that case, the insert probably would not bethought of as a zero-clearance insert.

Right portion 650 of insert 510 is larger than left portion 652 becauseopening 106 in the table is larger to the right of the blade than to theleft. Opening 106 is larger to the right of the blade so that a user mayreplace the blade, change the brake cartridge, or change between theriving knife and the blade guard through the opening, as described. Leftportion 652 is sized to provide some clearance between the blade and thetable and to provide additional room to adjust the position of mountingsystem 410 on the elevation plate when necessary.

Opening 106 in table 102 includes several support surfaces or pads 658spaced around the periphery of the opening as shown in FIG. 73, andinsert 510 rests on and is secured to those pads. Specifically, twoscrews 660 pass through right portion 650, one at each end, and theyscrew into threaded holes 662 in two of the pads 658. Two screws 664pass through left portion 652 and they screw into threaded holes 668.One of the holes in each of the right and left portions of the insertmay be oversized to facilitate the aligning of the screws with the holesin light of manufacturing tolerances. In the depicted embodiment, theholes to the back or rear of each of the right and left portions of theinsert are oversized. The screws are countersunk into the insert so theydo not extend above the surface of the insert. In this manner, the rightand left portions of insert 510 are secured in opening 106 and preventedfrom being accidentally knocked out of the opening by the spinningblade.

Right portion 650 is also secured in opening 106 by a flange 670 thatfits under a shoulder or edge of table 102. The flange prevents the backend of right portion 650 from moving up and out of the opening. Flange670 must be tucked under its corresponding shoulder when the insert isplaced in the table opening. Right portion 650 also includes a catch 672made from a projection that fits into and presses against a detent 674in left portion 652, as shown. Catch 672 may take many forms, includinga spring-biased ball that provides friction against the edge of leftportion 652, a snap fit, a magnet catch, etc. Flange 670 and catch 672are provided as an additional or alternative means to secure rightportion 650 in opening 106 because some users may not use the screws tosecure the right portion in the opening. They may not use the screws ifthey need to remove the right portion of the insert frequently to changeblades, change the brake cartridge, or switch between the riving knifeand blade guard. In that situation, it would be inconvenient torepeatedly screw and unscrew the right portion of the insert in thetable opening, so flange 670 and catch 672 are used to hold the rightportion in place.

Right portion 650 also includes a finger hole 680. A user may inserttheir finger into the hole to remove the right portion of the insertfrom the table opening.

Right portion 650 and left portion 652 include leveling screws 682 tolevel the insert relative to the tabletop. There are four levelingscrews in right portion 650 and three leveling screws in left portion652. The leveling screws are positioned over and rest against selectedones of pads 658. The leveling screws are spaced apart as shown in orderto provide both front-to-back and side-to-side leveling and to helpstabilize the insert.

The side-to-side position of insert 510 in opening 106 can be adjustedby a screw threaded into a hole 690 on the outside edge of right portion650. (Hole 690 is labeled in FIG. 100.) The screw can be threaded intothe hole so that it extends slightly beyond the outside edge of theinsert to increase the overall side-to-side dimension of the insert. Thefront-to-back position of the insert can be similarly adjusted by ascrew threaded into a hole 692 in the front edge of right portion 650.Additionally, the outer edge of left portion 652 includes two slightlyraised pads 694 that abut the corresponding inner edge of opening 106 tohelp position the insert in the opening.

Insert 510 also includes two metal plates 698 and 700 mounted on the topsurface of the insert at the back end with one pad on each side of slot656, as shown in FIGS. 95 and 96. Plates 698 and 700 may be attached tothe right and left portions of the insert, respectively, in many ways,such as by gluing. The metal plates are the surfaces on which theanti-kickback pawls described above may slide. The plates prevent theanti-kickback pawls from catching on or scratching the insert and thetabletop.

The top surface of insert 510 is typically made of a hard,non-conductive material such as melamine and it is often colored tocontrast with the tabletop.

The underside of right portion 650 includes a recessed section 702 alongthe edge of slot 656 and seam 654, as shown in FIG. 97. The recessedsection slopes back from the edge like a chamfer and provides clearancefor the blade when the blade tilts. Recessed section 702 and insert 510are designed for a left-tilting saw. The configuration could be mirroredfor a right-tilting saw. The underside of right portion 650 alsoincludes a recessed area 704 to provide clearance for the arbor and theblade washer and nut when the blade is fully elevated. The underside ofleft portion 652 also includes a recess 706 to provide clearance for thearbor block when the blade is fully elevated. The undersides of both theright and left portions of the insert may also include other recessedsections to minimize the mass of the part or to provide flattened orsmoothed areas to rest on pads 658. The recessed or smoothed areas maybe made by machining, molding or some other method.

INDUSTRIAL APPLICABILITY

The systems, mechanisms and components disclosed herein are applicableto power equipment, and particularly to table saws, including cabinetsaws, contractor saws, hybrid saws, jobsite saws, and bench top saws.

It is believed that the disclosure set forth above encompasses multipledistinct inventions with independent utility. While each of theseinventions has been disclosed in its preferred form, the specificembodiments thereof as disclosed and illustrated herein are not to beconsidered in a limiting sense as numerous variations are possible. Thesubject matter of the inventions includes all novel and non-obviouscombinations and sub-combinations of the various elements, features,functions and/or properties disclosed herein. No single feature,function, element or property of the disclosed embodiments is essentialto all of the disclosed inventions. Similarly, where the claims recite“a” or “a first” element of the equivalent thereof, such claims shouldbe understood to include incorporation of one or more such elements,neither requiring nor excluding two or more such elements.

It is believed that the following claims particularly point out certaincombinations and sub-combinations that are directed to one of thedisclosed inventions and are novel and non-obvious. Inventions embodiedin other combinations and sub-combinations of features, functions,elements and/or properties may be claimed through amendment of thepresent claims or presentation of new claims in this or a relatedapplication. Such amended or new claims, whether they are directed to adifferent invention or directed to the same invention, whetherdifferent, broader, narrower or equal in scope to the original claims,are also regarded as included within the subject matter of theinventions of the present disclosure.

The invention claimed is:
 1. A table saw comprising: a table defining awork surface, where the table includes an opening; a generally planar,circular blade configured to extend at least partially above the worksurface through the opening; a motor to drive the blade; a riving knifeor splitter having a base portion with opposing sides; an elevationcarriage supporting the blade and configured to move to change theelevation of the blade relative to the work surface with the blade at aspecific angular orientation relative to the work surface; and amounting system configured to hold the riving knife or splitter adjacentthe blade with the opposing sides of the base portion substantiallyparallel to the plane of the blade; where the mounting system issupported to move with the elevation carriage; where the mounting systemincludes a clamping structure; where the clamping structure includes afirst clamp surface and a second clamp surface, where the clampingstructure is configured to accommodate the base portion between thefirst and second clamp surfaces with the opposing sides of the baseportion generally adjacent the first and second clamp surfaces,respectively, where the clamping structure further includes a handleadapted to pivot around an axis below the work surface between a firstposition where the clamping structure does not clamp the base portionand a second position where the clamping structure clamps the baseportion, and where the clamping structure includes a cam systemconfigured to convert at least some pivotal motion of the handle intogenerally linear motion of at least one clamp surface toward the otherclamp surface; where the cam system includes a first cam surface at afirst pitch and a second cam surface at a second pitch different thanthe first pitch; where pivoting the handle from the first position tothe second position causes the first cam surface to convert pivotalmotion of the handle into generally linear motion of at least one clampsurface toward the other clamp surface after which the second camsurface stabilizes the clamping structure in the second position; wherethe handle can be pivoted by hand from one of the first position andsecond position to the other without using tools and without having topivot the handle more than one full revolution; where the first andsecond clamp surfaces are below the work surface; and where the handleand opening in the table are configured so that a user can access thehandle by reaching a hand through the opening.
 2. The table saw of claim1, where the first pitch causes one clamp surface to move toward theother clamp surface to clamp the base portion upon pivotal motion of thehandle, and where the second pitch does not cause further clamping ofthe base portion upon pivotal motion of the handle.
 3. The table saw ofclaim 1, where the first pitch causes one clamp surface to move towardthe other clamp surface upon pivotal motion of the handle to clamp thebase portion, but the second pitch does not.
 4. The table saw of claim1, where the cam system further comprises an edge between the first camsurface and the second cam surface.
 5. The table saw of claim 1, wherethe first and second cam surfaces are positioned around the pivot axisof the handle.
 6. The table saw of claim 1, where the second cam surfacehas a configuration and size to make the clamping structure stable withthe handle in the second position.
 7. The table saw of claim 1, wherethe first pitch has slope relative to the second pitch, and the secondpitch is generally flat relative to the first pitch.
 8. The table saw ofclaim 1, where the mounting system includes a pin extending out from oneof the clamp surfaces, where the base portion of the riving knife orsplitter includes an opening to receive the pin, and where the first andsecond clamp surfaces are spaced sufficiently apart with the handle inthe first position for the riving knife or splitter to be moved off ofthe pin.
 9. The table saw of claim 1, where the handle is generallyelongate with an end section adjacent the axis around which the handleis adapted to pivot.
 10. The table saw of claim 1, where the clampingstructure further includes a bolt and a spring positioned around atleast a portion of the bolt, where each of the first and second clampsurfaces includes an aperture through which the bolt passes, where thefirst clamp surface is part of a first plate, where the second clampsurface is part of a second plate, and where the spring contacts atleast one of the first and second plates.
 11. The table saw of claim 10,where the bolt is positioned generally along the axis around which thehandle is adapted to pivot, and where the handle is generally elongatewith an end section adjacent one end of the bolt.
 12. A table sawcomprising: a table defining a work surface, where the table includes anopening; a generally planar, circular blade configured to extend atleast partially above the work surface through the opening; a motor todrive the blade; a riving knife or splitter having a base portion withopposing sides; an elevation carriage supporting the blade andconfigured to move to change the elevation of the blade relative to thework surface with the blade at a specific angular orientation relativeto the work surface; and a mounting system configured to hold the rivingknife or splitter adjacent the blade with the opposing sides of the baseportion substantially parallel to the plane of the blade; where themounting system is supported to move with the elevation carriage; wherethe mounting system includes a clamping structure; where the clampingstructure includes a first clamp surface and a second clamp surface,where the clamping structure is configured to accommodate the baseportion between the first and second clamp surfaces with the opposingsides of the base portion generally adjacent the first and second clampsurfaces, respectively, where the clamping structure further includes ahandle adapted to pivot around an axis perpendicular to the opposingsides of the base portion of the riving knife and below the work surfacebetween a first position where the clamping structure does not clamp thebase portion and a second position where the clamping structure clampsthe base portion, and where the clamping structure includes a cam systemconfigured to convert at least some pivotal motion of the handle intogenerally linear motion of at least one clamp surface toward the otherclamp surface; where the clamping structure further includes a bolt anda spring positioned around at least a portion of the bolt, where each ofthe first and second clamp surfaces includes an aperture through whichthe bolt passes, where the first clamp surface is part of a first plate,where the second clamp surface is part of a second plate, where thespring contacts at least one of the first and second plates, and wherethe bolt is positioned generally along the axis around which the handleis adapted to pivot; where the handle can be pivoted by hand from one ofthe first position and second position to the other without using toolsand without having to pivot the handle more than one full revolution;where the first and second clamp surfaces are below the work surface;and where the handle and opening in the table are configured so that auser can access the handle by reaching a hand through the opening.